BUILD a better pizza, as the saying might go, and people will beat a path to your door. But if it's Saturday night they'll have to reserve four weeks ahead.

That's true in Los Angeles, anyway, where America's most famous, perhaps most expensive and, some argue, most delicious pizza is being made. It's the creation of chef Wolfgang Puck, who, true to his name, keeps coming up with surprises. Last year he left Ma Maison, where he had won his reputation, and opened his first restaurant, Spago, where the pizza itself has celebrity status; and this year he's deep into the planning of Chinoiserie. "Americans are tired of French food," yawns Puck. "I think sometimes if you give them corn muffins they will be happier than hearing about another beurre rouge."

To prove it, he grossed a million dollars in the first year with Spago, where he added 35 seats in a heated tent to take care of the overflow from his 100 seats. To an average of 250 diners a night he serves 120 pizzas, but that is just the first course, for diners generally go on to grilled baby lamb with wild rosemary or grilled fresh tuna on a bed of raw tomatoes and mint. And they wind up spending nearly $40 a person. True, Spago has an extraordinary view of the city--if you have a front window table. And true, Victoria Principal had her birthday party there with Cher, the same night Peter Falk was dining and the night after Sidney Poitier had been in for dinner. And true, the restaurant is decorated with $800 worth of flowers a week and they don't even eclipse the snazzy modern art on the walls.

But Spago remains famous for its pizza. What could a pizza have that Sidney Poitier or Peter Falk can't outshine? Toppings of fresh wild mushrooms--four kinds. Goat cheese and buffalo mozzarella. Homemade sausages of duck and of lamb. Prosciutto, Black Forest ham, smoked salmon, fresh Santa Barbara shrimp. Even caviar. No pepperoni.

The most popular of Puck's pizzas is prosciutto with goat cheese, Italian tomatoes, red bell peppers, red onion and "double-blanched" garlic. But even that doesn't tell the story. These are pizzas baked in a wood-burning oven, using oak, cherry, apricot or grape branches. And they are made of dough that takes 1 1/2 to 2 hours after the basic mixture--flour, yeast, virgin olive oil, honey and salt--is concocted. The dough is rolled as thin as possible (and only eight inches across, since each pizza serves as one appetizer), so the pizza "is not just dough," says Puck. If tomatoes are included on the pizza, they are fresh Italian plum or sun-dried tomatoes. If it's onions, they are red onions or maybe shallots.

There is a limit to the lengths one should go, Puck has learned. "If you try to make them too complicated it doesn't work," he says with resignation, though his idea of simple is not everybody's idea of simple. But even a $8 or $9 eight-inch pizza "should stay earthy. It's not a dish that improves from refinement."

It is a dish, conclude those who have tasted Puck's recipe (below), that makes grossing $3 million believable, and could be improved only if your home kitchen had a wood-burning oven. SPAGO PIZZA (4 8-inch pizzas) Dough: 1 package active dry yeast 1 1/4 cups water 1 teaspoon salt 1 teaspoon sugar (substitute 1/2 teaspoon honey) 4 cups flour 2 tablespoons virgin olive oil Toppings: 1 1/2 pounds buffalo mozzarella 1/2 pound fontina cheese 10 Italian plum tomatoes 1 clove garlic, peeled 1/4 cup virgin olive oil 6 ounces prosciutto, cut into fine julienne 2 tablespoons chopped fresh basil 1 red onion, minced finely 2 red bell peppers, minced and saute'ed in olive oil 6 ounces fresh goat cheese

Make the dough by activating yeast in 1/4 cup warm water and set aside. Dissolve sugar or honey and salt in 1 cup of warm water. Add flour and oil and mix with hands for 1 minute and then add the dissolved yeast.

Mix or knead about 10 minutes, or until dough is smooth and no longer sticks to fingers or mixing bowl. Set aside for 1 hour, covered with a damp cloth.

Prepare toppings. Grate or finely chop buffalo mozzarella and fontina cheese, mix together and set aside. Slice plum tomatoes. Blanch garlic in water and chop coarsely.

Divide dough into 4 equal parts. Roll and stretch into 8-inch circles. Brush the top with olive oil; sprinkle with chopped basil. Spread the cheese mixture evenly. Add tomatoes, prosciutto, red onion, peppers and garlic. Top each pizza with bits of goat cheese.

Bake in 400-degree oven for approximately 35 minutes or until the dough is golden brown on top and bottom.