Instructions

1. First, make the cake. Preheat the oven to 350°F. Line the bottoms of three 8-inch round cake pans with parchment paper and grease the sides with cooking spray. Set aside.
2. In a stand mixer fitted with the whisk attachment, add the butter and oil and beat on low speed until combined so the oil doesn’t fly everywhere. Add the granulated sugar and gradually increase the speed to medium-high and beat until light and fluffy, about 2 minutes.
3. Use a silicone spatula to scrape down the sides and bottom of the bowl, then add the eggs, vanilla, and almond extract. Beat on medium-high speed until the mixture is pale and creamy, about 2 minutes.
4. In a separate mixing bowl, add the flour, baking powder, and salt and whisk to combine. With the mixer on low speed, add half of the dry ingredients, then all of the buttermilk, then the remaining half of the dry ingredients. It’s okay if the batter still has a few lumps—you don’t want to overmix.
5. Divide the batter evenly between the prepared pans and bake until the cakes have risen, the tops spring back to the touch, and a butter knife inserted in the center of the cake comes out with just a few moist crumbs attached, 20 to 25 minutes. You can leave the oven on! You’ll use it to make the crumble pieces.
6. While the cakes are cooling, make the brown sugar crumble pieces. Line a baking sheet with parchment paper. In a medium bowl, add the flour, brown sugar, melted butter, vanilla, and salt. Use a silicone spatula to mix until combined. 
7. Squeeze the mixture into your palms, then break it apart into big and small clusters over the prepared baking sheet. Bake in the pre-heated 350°F oven until the crumble pieces turn golden brown, about 15 minutes, using the silicone spatula to stir halfway through. Place the pan onto a cooling rack, allowing to cool completely.
8. Next, make the blackberry filling. In a medium bowl combine most of the blackberries (leaving a few out to garnish the top of the cake later) and blackberry jam. Use a spoon to stir to combine.
9. Once everything is fully cool, make the frosting. In a stand mixer fitted with the paddle attachment, add the butter and cream cheese and mix on medium speed until combined, about 30 seconds. Use a silicone spatula to scrape down the sides and bottom of the bowl, then add the powdered sugar, vanilla, and salt and beat on medium-high speed until light and fluffy, about 1 minute.
10. Assemble the cake. Place the first cake layer onto a cake stand or serving plate. Top with about 1/4 of the frosting and use an offset spatula to spread it evenly to the edges, making a divot that slopes toward the center so the edges are slightly higher than the center (this keeps the filling from spilling out). Top with about 1/2 of the blackberry filling, then sprinkle with 1/2 of the crumble pieces. Repeat with the second layer of cake, topping with frosting, blackberry filling, and crumble pieces. Top with the third layer of cake, use the remaining frosting to frost the top and sides of the cake, then sprinkle the top with the remaining crumble pieces and garnish with blackberries or dollops of jam. Cake is best served at room temperature. If not serving within 2 to 3 hours, store in the fridge until ready to serve.