1 1⁄2 cups buttermilk
1⁄2 cup yogurt (we prefer to use full-fat plain Greek yogurt)
2 large eggs
1⁄2 cup canola oil
1⁄3 cup turbinado sugar (natural brown sugar)
1 1⁄2 teaspoons pure vanilla extract
1 1⁄2 cups rolled oats
3⁄4 cup whole wheat flour
3⁄4 cup spelt flour
2 1⁄4 teaspoons baking powder
2 1⁄4 teaspoons baking soda
1⁄2 teaspoon kosher salt
1⁄2 teaspoon ground allspice
1⁄2 teaspoon ground cardamom
1⁄2 teaspoon ground ginger
1 1⁄2 cups all-purpose flour
3⁄4 cup packed light brown sugar
1 1⁄2 teaspoons ground cinnamon
1⁄2 teaspoon kosher salt
3⁄4 cup (1 1⁄2 sticks) unsalted butter, straight from the fridge
1 1⁄2 cups sliced peaches
1 cup blackberries
6 ounces cream cheese, at room temperature, divided into 12 equal pieces
2 tablespoons Sugar-Sugar (a Sister Pie original ingredient blending equal parts turbinado and granulated sugars)
Mix the batter: In a medium bowl, whisk the buttermilk, yogurt, eggs, canola oil, turbinado sugar, and vanilla until the ingredients are homogeneous and smooth. In a large mixing bowl, whisk together the oats, whole wheat and spelt flours, baking powder, baking soda, salt, allspice, cardamom, and ginger, then add the wet ingredients. Use a silicone spatula to gently fold in the wet ingredients until no dry spots remain. Cover the bowl with plastic wrap or a lid and place in the refrigerator overnight or for at least 20 minutes.
Make the streusel: Combine the flour, brown sugar, cinnamon, and salt in a large stainless steel bowl. Place the butter in the bowl and coat on all sides with the flour mixture. Use a bench scraper to cut the butter into 1⁄2- inch cubes directly into the flour mixture in the bowl. Work to break up the cubes with your hands until they are lightly coated with the flour mixture. Continue to use the bench scraper to cut the cubes into smaller pieces— the idea is that you are cutting each cube in half.
Switch to a pastry blender and begin to cut in the butter with one hand while turning the bowl with the other. It’s important not to aim for the same spot at the bottom of the bowl with each movement, but to actually slice through butter every time to maximize efficiency. Once most of the butter is incorporated, use your fingers to fully break down the butter until the streusel resembles wet sand. The streusel can be prepared up to 2 days in advance and stored in the refrigerator before assembling and baking.
Preheat your oven to 400°F. Line a 9 by 13- inch baking pan with parchment paper, leaving an overhang of 1 to 2 inches so you can easily lift the coffee cake out of the pan after cooling.
Use a silicone spatula to transfer the batter to the baking pan. Use a knife or offset spatula to evenly spread the batter across the pan, making sure to smooth it from edge to edge. Evenly cover the batter with the peaches and blackberries, then distribute the 12 pieces of cream cheese over the batter, placing 4 pieces across the long sides of the pan and 3 along the ends of the pan, and so forth. Sprinkle with the Sugar- Sugar, then use the offset spatula to gently press the cream cheese down into the batter. Cover with the streusel. It’s okay if some of the fruit is still visible. In fact, it’s better than okay.
Place the baking pan in the oven and bake for 35 to 40 minutes, until a knife inserted into the middle of the coffee cake comes out clean. Remove the pan from the oven and set it on a wire rack to cool. Once the bottom of the pan is at room temperature, carefully lift the coffee cake out of the pan and onto a cutting board, using the parchment overhang for handles.
Use a sharp chef’s knife to cut the coffee cake into 16 pieces. Store leftover coffee cake in an airtight container in the refrigerator for up to 2 days.
Recipe reprinted with permission from “Sister Pie,” copyright 2018. Published by Lorena Jones Books, an imprint of Penguin Random House.