THE COBBLER TOPPING: Cut the butter into ½-inch cubes. In a food processor, pulse the butter, flour, cornmeal, sugar, and salt until the mixture resembles coarse meal. Remove the mixture to a bowl, and add the ice water, a spoonful at a time. With a wooden spoon stir until just combined. Roll out the dough to ½-inch thickness, and cut into shapes using a knife or cookie cutter. Lay the pieces on a cookie sheet, and refrigerate while preparing the filling.
THE FILLING: Heat the oven to 350°F. Pit and peel the peaches, and cut into ¾-inch-thick wedges (peeling is optional). In a large bowl toss the peaches, raspberries, sugar, cornstarch, ginger, and lemon juice. Pour the fruit into a large ungreased baking dish or small individual ramekins.
Arrange the dough shapes on top of the fruit. Brush the dough with the yolk and sprinkle with sugar. Bake until the top is golden, about 30 minutes. Let cool until warm.
THE FROMAGE BLANC GELATO: In a small saucepan over high heat, combine the sugar and water, and bring to a simmer for 5 minutes. Cool completely. You should have 2 cups simple syrup. In a bowl combine the simple syrup, fromage blanc, yogurt, and corn syrup until well blended. Freeze in your ice cream maker according to manufacturer’s directions. Serve a scoop alongside a warm portion of cobbler.