Peach Pistachio Galette

To make the dough, combine flour, sugar, cornmeal, and salt in a processor; pulse 2-3 times. Add butter and pulse 4-5 times, or until mixture resembles coarse meal. With the processor running, slowing pour the buttermilk through the chute, processing until the dough forms a ball. Remove dough ball and adhere any remaining pieces of dough to it, then wrap in plastic wrap or parchment paper. Refrigerate for at least 45 minutes before rolling out. Center a rack in the oven and preheat to 350 ºF. Remove galette dough from the refrigerator and place on a sheet of parchment paper. Starting at the center of the dough, roll out, forming a 14- to 15-inch wide circle. Place the dough with parchment paper on a baking sheet. Arrange peach slices on top of the dough, leaving a 2-inch border. Sprinkle chopped pistachios over peaches. Fold dough border over peaches, overlapping where necessary and pressing gently to adhere the folds. Drizzle peaches with honey. Using a pastry brush, lightly brush the edge of the dough with the beaten egg. Place galette on a large baking sheet, with the parchment paper. Bake galette for 45 minutes, or until crust is golden brown. Transfer baking sheet to a wire rack and let galette cool to room temperature before slicing. Slice and top with vanilla ice cream, if desired. Note: You can make the galette dough in advance. It will keep in the refrigerator for 3 days. You can also freeze the dough for up to one month. Defrost the frozen dough before rolling out.