Serves: Makes 8 servings
- ¾ cup unbleached all-purpose flour
- 3 tablespoons brown sugar
- 2 tablespoons granulated sugar
- ¼ teaspoon ground cinnamon
- Pinch of kosher or sea salt
- 6 tablespoons unsalted butter, cool but not chilled, cut into 12 pieces
- ½ cup coarsely chopped toasted walnuts
- ⅓ cup old-fashioned rolled oats
- 1½ to 1¾ pounds peaches, peeled, halved, pitted, and cut into ½-inch chunks
- ½ pound rhubarb, trimmed and cut crosswise into½-inch pieces
- ½ cup plus 2 tablespoons granulated sugar
- 2 tablespoons quick-cooking tapioca
- To make the topping, put the flour, brown sugar, granulated sugar, cinnamon, and salt in a stand mixer fitted with the paddle. Mix on low speed until well blended. Add the butter and mix until the mixture resembles coarse crumbs. On medium-low speed, add the walnuts and oats and mix until the mixture begins to clump, 2 to 3 minutes. You can also prepare the topping in a food processor, but the mixer is preferable. Set aside.
- Preheat the oven to 375°F. Put the peaches, rhubarb, granulated sugar, and tapioca in a large bowl and stir to blend. Let stand for 10 minutes to draw some juices from the fruit.
- Transfer the fruit to a 10-inch pie pan or other baking dish of similar capacity and spread it evenly. Sprinkle the topping evenly over the surface. Put the pie pan on a baking sheet to catch any drips.
- Bake until the topping is nicely browned and the filling is bubbling, about 50 minutes. Cool on a rack. Serve warm, not hot.