For the filling: 1 onion, chopped fine (preferably in a food processor) 1-1/2 lbs. mushrooms, chopped fine (preferably in a food processor) 2 tablespoons unsalted butter freshly grated nutmeg to taste 1-1/2 cups heavy cream 3 large eggs Make the shell: Roll out the dough 1/8 inch thick on a lightly floured surface, fit it into a 10-inch tart pan with a removable fluted rim, and chill the shell for 30 minutes. Line the shell with foil, fill the foil with the rice, and bake the shell on a preheated baking sheet in the lower third of a preheated 425° F. oven for 12 minutes. Remove the rice and foil, brush the shell with some of the egg, and bake it for 5 to 10 minutes more, or until it is golden. Let the shell cool in the pan on a rack. Make the filling: In a large heavy skillet cook the onion and the mushrooms in the butter with the nutmeg and salt and pepper to taste over moderate heat, stirring, for 10 to 15 minutes, or until the liquid the mushrooms give off is evaporated, and let the mixture cool. Whisk in the cream, the eggs, and salt and pepper to taste. Pour the filling into the shell and bake the flan in the middle of a preheated 350° F. oven for 30 to 35 minutes, or until the filling is firm. Let the flan cool in the pan on the rack and remove the rim. Serve the flan warm or at room temperature. brunch 27