1 cup plus 2 tablespoons all-purpose flour
2 tablespoons packed light brown sugar
1 1/2 teaspoons baking powder
1/4 teaspoon baking soda
1/8 teaspoon fine salt
4 tablespoons unsalted butter (1/2 stick), frozen
1/4 cup sour cream
2 tablespoons heavy cream
1/4 cup all-purpose flour
1/2 cup packed light brown sugar
1/4 cup granulated sugar
1/8 teaspoon fine salt
1 vanilla bean, split lengthwise and scraped, seeds reserved
1 1/2 pounds peaches, pitted and cut into sixths (about 5 cups)
12 ounces blackberries (about 2 1/2 cups)
2 teaspoons sour cream
1 tablespoon coarse sanding sugar (can substitute granulated sugar)