Preheat oven to 425 degrees F. Butter one cookie sheet with 3/4 inch sides.
In a 3 to 4 quart saucepan, heat to scald milk, salt and 6 tablespoons butter. Pour in polenta in a thin stream, whisking vigorously, and cook for about a minute, switching to a wooden spoon as polenta thickens. Remove from heat and stir in 1/2 cup grated cheese and 4 egg yolks and mix well. Pour polenta in buttered cookie sheet and spread to a thickness of 1/2 inch. Allow to cool.
Using a pastry cutter or water glass, cut 3 inch quarter moons out of the polenta. Arrange leaning up against one another in a buttered baking dish and sprinkle with remaining grated cheese. Place in oven and cook 15 to 20 minutes, or until top is light golden brown. Remove and serve immediately.
Recipe courtesy of Mario Batali