The Milk Street Cafe has been sold again. This makes the fifth year in a row it has changed hands in a most unusual transaction. This elegant cafeteria tucked away in the caverns of Boston's financial district at 50 Milk Street is owned 51 weeks of the year by Mark Epstein, who has fashioned a menu that is both kosher and vegetarian.

But alas. When Passover comes, as it does tonight, Epstein must forsake every crumb of yeast bread to obey Jewish dietary laws for the holiday.

"Easiest by far would be to close the doors for those eight days," said Epstein, an energetic, good-humored young man of 28, "but the lease I signed in the beginning says we must stay open 52 weeks a year so the building's tenants will have a place to eat whether it rains or shines. That's fair, so I decided to find a way."

He took the problem to a local rabbi, famous for his wisdom, who suggested that Epstein sell the restaurant to his non-Jewish staff for Passover, and have it revert to him the day after. To make sure that Jewish customers are aware of what is going on, he posts signs that say "Not Kosher for Passover."

"It's all symbolic," Epstein said, "a way to remember the time about 4,000 years ago when Moses led the Jews out of slavery in Egypt. They fled before the bread had time to rise. And these days, matzo must be baked within 18 minutes after the dough is formed to make sure it hasn't risen."

If the Milk Street Cafe did stay open, every nook and cranny would have to be searched for the tiniest crumb of yeast bread, and the menu would have to be changed drastically. A Mushroom Melt on a matzo instead of tucked into pita bread? The two soups of the day are always served with a generous chunk of warm bread in a number of grain flavors, and that would disappear. How austere the financiers' breakfasts would be.

Everything about the Milk Street Cafe is understated, like those banks in the neighborhood that only want millionaire clients. The entrance quietly announces its existence with white etching on the glass in a ribbon of letters that repeats the restaurant's name until the space runs out. Inside are three small dining rooms jammed with tables and chairs of light lacquered wood, and a cafeteria line that is short and efficient with a separate line for take-out business.

Obviously the restaurant is doing everything right. Boston Magazine tapped it for its Best of Boston issue in two consecutive years -- once in 1984 for Best Cafeteria and last year for Best Soup and Salad Restaurant. Neither kosher nor vegetarian was ever mentioned.

Doors open at 7 a.m. and the waves of men and women wearing power suits begin. Epstein appears in shirt sleeves and a comfy sweater vest of many colors. His staff favors dark blue shirts and slacks in washable cotton.

One hesitates to call the Milk Street Cafe a dairy restaurant, although it qualifies in every way -- not a kreplach in sight, no bowls of sour cream or half sour pickles on the tables, and if mushroom-barley soup appears on the menu it will be distinctly the Milk Street Cafe's rendition.

"The food isn't supposed to be Jewish," Epstein said. "It's vegetarian so there's no meat, and we buy ingredients from kosher suppliers." Pizza -- a Friday standard -- is what Bostonians call "Chicago style," a deep-dish pie with a partly whole-wheat crust and a generous amount of kosher mozzarella, parmesan, tomato sauce and mushrooms.

The brisk MBAs who flood the restaurant can comfort themselves with familiar food at lunch to give them strength for the trendy mysteries of rare duck breast and three shades of caviar they'll have to learn to love at night. The Milk Street Cafe cuisine could be described as Late Whole Earth Catalogue, a pinch of California-Berkeley, and a dusting of healthful eating from the serious '70s. Sandwiches bristle with alfalfa sprouts and also come with fresh tomato, lettuce, and sliced onion if you tell the server. Carrot cake with cream cheese frosting is featured daily. Cookies span six or seven inches.

When Esptein signed that famous first lease, he was a recent graduate from intellectual's heaven, Brandeis University in Waltham, Mass., where he studied history and economics. "I decided to stay out and earn the money for a graduate degree, planning to go back when I was 30. A restaurant seemed the best way to do it. I've always believed in hospitality. Our house was the place where everybody gathered, and I thought I could recreate this feeling in a restaurant that served delicious food."

Last year Epstein opened another Milk Street Cafe in Cambridge, but this lease allows him to close for all the Jewish holidays. Two restaurants are enough, and now he is concentrating on his catering department which is directed by Susan Gilmore.

"Mostly we do parties for the offices in the neighborhood," Gilmore said, "deli platters and sandwiches and desserts, but many people don't seem to realize that we're vegetarian or kosher. They'll start out asking for a platter of roast beef or salami."

Forty-one people are on the payroll, and work starts at 10 every night when the bakers come in. "They get through a lot of bread and danish and desserts," Epstein said, "and then the cooking crew comes in at 5:30 to start the soups and salads."

The Milk Street Cafe is open Monday through Friday from 7 a.m. to 3 p.m. and every day about 2,000 people go through the line. How much time is left for Epstein's private life?

"Are you married?" I asked.

"I'd like to be. I just haven't found the right girl."

"You're still young. It'll happen."

He smiled, probably accustomed to such motherly reassurances. "From your lips to God's ears," he said.

These recipes for Passover are from Mark Epstein's mother Anita in Worcester.

GEFILTE FISH (8 to 10 servings as an appetizer)

4 pounds whole fish -- pike and whitefish -- filleted, with skin and bones reserved

4 large onions

3 large eggs

1 1/2 tablespoons kosher salt

3/4 teaspoon black pepper

1/4 cup matzo meal (see instructions)

3 carrots

Grind the fish fillets and 2 onions, then mix in the eggs with a fork, adding 1/2 tablespoon of salt and 1/4 teaspoon black pepper. Stir in matzo meal. Using a hand chopper, continue to chop the mixture until it is sticky, adding 1/4 cup of water as you go. (Anita Epstein suggests that you grind the fish and onions, but do the chopping in a food processor, eliminating the matzo meal.)

Line a 6-quart pot with the skin and bones. Slice the remaining 2 onions and the carrots and arrange them on the bones. Sprinkle with 1 tablespoon salt and 1/2 teaspoon pepper. Add water to cover and bring to a boil. Make 16 to 20 balls with the fish mixture, forming them with wet hands, and drop them into the boiling stock. Cook over medium heat for 1 1/2 to 2 hours. Remove pot from the fire and cool the gefilte fish to room temperature. Store gefilte fish balls and broth in the refrigerator. To serve, garnish each plate with a little of the jellied stock, a slice or 2 of carrot.

CHOPPED LIVER (Makes 3 cups)

1 pound beef liver in 2 slices

Kosher salt to taste

3 large onions

2 tablespoons vegetable oil

2 hard-cooked eggs

1 tablespoon mayonnaise

Pepper to taste

Lightly salt the liver and broil until well done. Wash off the liver, cool to room temperature and cut in small pieces.

Cut a 1/4-inch slice from one of the onions and reserve. Chop the remaining onions coarsely and saute' in vegetable oil until golden. Cool to room temperature.

Grind liver, saute'ed onion, the small piece of raw onion, and eggs. Fold in the mayonnaise and season with salt and pepper to taste.

CHICKEN SOUP (Makes about 2 quarts)

4- to 5-pound chicken, cut in eighths

4 medium onions

6 carrots

3 stalks celery with leaves

2 parsnips

1 tablespoon kosher salt

1/2 teaspoon white pepper

Wash and clean the chicken pieces. Place them in a 6-quart pot with all the vegetables and seasonings. Cover with boiling water and simmer gently for 2 hours or until the chicken is tender. Remove pan from the heat and let the broth cool. Reserve the chicken and discard the vegetables. Refrigerate the broth and remove the fat before reheating with the matzo balls.

MATZO BALLS (Makes 16 balls)

4 eggs

1 teaspoon salt

1/4 cup melted shortening

1/4 cup water or chicken broth

1 cup matzo meal

In a small bowl, beat the eggs; add salt, shortening and the chicken broth or water, and then the matzo meal. Refrigerate for at least 1/2 hour.

Bring 3 quarts of salted water to a boil in a 4- or 5-quart pot. Form 16 balls from the matzo mixture with wet hands and drop into the boiling water. Lower the heat and cook for about 1 hour -- even longer. Anita Epstein says that this is the secret for really light matzo balls. Transfer them to the chicken stock with a slotted spoon and heat altogether for a few minutes.

FRUIT COMPOTE (8 to 10 servings)

3 pounds mixed dried fruit

1 apple, peeled and sliced thin

1 pear, peeled and sliced thin

1 orange, unpeeled and sliced thin

1 lemon, unpeeled and sliced thin

Sugar to taste

1/2 teaspoon cinnamon

Put all of the fruits into a pot, add water to cover by 1 1/2 inches, cover and bring to a boil. Stir in sugar to taste, add the cinnamon and simmer for about 3 minutes. Remove from the burner and cool to room temperature.

CHOCOLATE CAKE (Makes one 10-inch tube cake)

10 large eggs, separated

1 1/3 cups sugar

1/2 cup sifted matzo cake meal

1/4 cup sifted potato starch

1/2 teaspoon instant coffee

1 teaspoon cocoa

1/4 cup orange juice

1 teaspoon orange rind

1 cup finely chopped walnuts

4 ounces bittersweet chocolate, grated

Combine yolks and 1 cup of sugar in the bowl of an electric mixer and beat until light and fluffy, about 10 minutes. Sift together the cake meal, potato starch, instant coffee, and cocoa. Add orange juice and orange rind alternately with the sifted dry ingredients to the egg yolk mixture, folding them in carefully.

In a separate bowl, beat egg whites until they form soft peaks. Add 1/3 cup of sugar a teaspoon at a time; continue to beat until stiff peaks form. Fold yolk mixture into whites; fold in nuts and chocolate, working swiftly and gently to keep from breaking egg whites. Bake in an ungreased 10-inch tube pan in a 350-degree oven for 1 hour. Invert pan to cool.