I've always liked the unlikely combinations. The old Laurel and Hardy Syndrome. I still recall the moment in third grade when my closest friend invited me to sample his peanut butter and mayonnaise sandwich. Panut butter and what? I took a alternative taste. Hummmm . . . not bad at all. Another taste . . . well, not as bad as might be.

A more recent example, I was in a world-famous Mexican restaurant. The menu was filled with these incongruous combinations. Aha . . . chocolate-covered turkey. It sounded singularly unpromising and looked no better, as though someone had melted a box of bonbons over a half a turkey. Well, you can imagine my surprise, on finally digging into it, to discover that what you saw was you got, one of the most thoroughly repuguant concoctions conjured up in this hemisphere.

Today, another of those unlikely pairings. But this one is an unqualified winner. It's known as Vitello Tonnato. The reason I do not use the English translation: We would want to eat something called Veal with Tuna Fish Sauce?

The Staples: Make sure these are all on hand: salt, pepper, peppercorns, bay leaves, olive oil, eggs, garlic, butter.

The Shopping List: Boneless leg of veal (approximately 3 pounds, tied by butcher); 1 small can of anchovies; 1 bottle dry white wine; 1 small bottle capers; canned chicken consomme (2 cups); canned white-meat tuna (approximately 6 ounces); heavy cream (1/2 pint container); long-grain white rice; 3 onions, carrots (2 pounds); 2 lemons; 1 bunch scallions; celery, parsley, fruit in season.

Although Vitello Tonnato is a summer time favorite, don't let the season scare you off. In fact, there are as many ways to prepare this as there are restaurants in Italy: It can be served cold or hot; the meat can be boiled or baked; the sauce invites experimentation. We'll try one of the easier ways to cook the dish. It takes somewhat longer - 48 hours in all - but leaves little to chance.

Prepare Two Days in Advance: The marinade for the meat.

Using a large pan, heat 4 tablespoons of olive oil over medium heat. Add an onion, cut into small pieces. Also 2 stalks of celery, including some of the leaves, chopped fine; 3 carrots, peeled and chopped. Cook these until the onion becomes tender. Add 1/2 the bottle of white wine and bring to a boil. As the liquid is coming to a boil, add 3 bay leaves: 10 peppercorns; several sprigs of parsley; a large pinch of salt. Allow this to boil for 10 or 15 minutes. Then, as you add the piece of veal, turn the heat off.

When the liquied has cooled sufficiently, regrigerate, allowing the meat to marinate overnight in the wine broth. Occasionally turn the piece of meat over.

Prepare One Day in Advance: The meat. Preheat oven to 375 degrees. Remove the meat from the marinade and put it into a roasting pan that has been greased with butter. Put roasting pan in oven for just 1 hour. Occasionally baste the meat with some of the marinade while it is roasting.

Later, as the meat is cooling, make the sauce. The sauce should be about the same consistency as cream. It will be easiest to make if all the ingredients are at room temperature.

Put 2 egg yolks into the blender. Add 1 cup of olive oil; the tuna fish, drained of all oil; the juice of 2 lemons and the anchovies. Turn on blender and mix until all this forms a heavy, smooth sauce. Now add enough of the heavy cream to thin it out. Put a small amount of the sauce along the bottom of a shallow platter.

When the meat has cooled, cut it into thin slices and arrange it across the platter. Cover with the remainder of the sauce, making sure that each piece of meat is thoroughly coated with the sauce. Cover it with a clear plastic wrap and store it in the refrigerator until ready to serve.

5:15 P.M.: The rice pilaf. Using a small pan, melt 1/2 stick of butter over medium heat. Add 1 onion, chopped fine; 2 cloves or garlic, minced; a pinch of salt and some peper.

When onion is tender, add 1 cup of the long-grained rice and allow it to heat for a couple of minutes. Then add 2 cups of chicken consomme and bring it to a quick boil. Turn the heat down to low, cover the pot and allow the rice to cook for just 25 minutes. Then turn off heat.

Now is a good moment to remove the meat from the refrigerator and allow it to come to room temperature.

6 P.M.: Peel and slice the rest of the carrots. Melt 1/2 stick of butter in a large frying pan over medium heat. Add the slice carrots. And the scallions - whites and some of the greens - chopped fine. Now some salt, some pepper and a squeeze of lemon juice. Cook over medium-low heat until carrots are tender.

6:30 P.M.: Remove the meat slices from the platter, arrange them on a serving dish and drape the sauce over them. Garnish with a small handful of carpers, sprigs of parlsey and some lemon sections.