These tarts should be crisp on the edges and have a generous proportion of fruit to dough. They can be returned to the oven for 5 minutes to reheat before serving. FOR THE DOUGH:
1/4 cup sugar (superfine if possible)
1 cup milk
1 package active dried yeast
6 egg yolks
3 1/2 to 4 cups unbleached flour
1 teaspoon salt
5 tablespoons unsalted butter, softened
1 cup currants (or raisins) FOR THE TOPPING:
1 lb. mascarpone (a soft, sweet, white cream cheese; try a gourmet grocery store)
2 cups brown sugar
Seedless red grapes or pitted cherries
Heat sugar and milk to lukewarm. Whisk yolks lightly and combine with warm milk mixture. Combine yeast with the flour and salt. Form a well in the center of the flour mixture and pour in liquid. Mix to a dough either with a wooden spoon or in an electric mixer with a dough hook. Beat well. Divide the softened butter into three or four pieces and add one piece at a time, beating hard after each addition.
Continue to beat in mixer until dough is smooth, shiny, and comes away from the sides of the bowl cleanly, or turn out onto a floured surface and knead by hand. Dough will be sticky.
Place dough in a well-buttered mixing bowl, turning to coat. Cover with towel or plastic wrap and let rise until it doubles in size, 1 to 2 hours. When well-risen, tip onto a floured surface, scatter over the currants, and knead to mix through evenly.
Divide dough into 16 equal-sized pieces and roll each piece into a ball. Place seam-side down on a greased baking sheet, preferably one with a rim. Leave plenty of room between the balls (you will need more than one sheet).
Press each ball out flat to about 1/2 inch thickness. Spread each tart with about 2 tablespoons mascarpone cheese and pile on a handful of seedless grapes or pitted cherries. Push the fruit in firmly to flatten the dough.
Sift a generous covering of brown sugar (about 2 tablespoons) on each tart. Bake in a 400-degree F. oven for 20 minutes.
Makes 16 tarts.