Preheat oven to 350 degrees. Grease and flour an 8-inch round or square pan. Set aside.
In a medium bowl, whisk together the flour, baking powder, baking soda and salt. Set aside.
In the bowl of a standing mixer fitted with the paddle attachment, cream the butter and sugar on high speed for 3 minutes or until light and fluffy. Scrape down the sides with a spatula.
Reduce mixer speed to low and add the egg, vanilla paste, mashed bananas and sour cream. Mix until combined.
Slowly add the flour mixture and mix until until combined.
Transfer the batter to the prepared pan and smooth the top.
To make the streusel, add the brown sugar, flour, cinnamon, salt and butter to a bowl. Using your fingers, pinch together the ingredients until the mixture is in crumbles. Distribute evenly over the cake batter.
Sprinkle the chocolate chips and almonds on top of the streusel. Bake for 40 to 45 minutes or until a tester inserted in the center comes out clean. Cool in the pan.
Serve warm or at room temperature.
This is my adapted version of Ina Garten's Chocolate Banana Crumb Cake from "Make it Ahead: A Barefoot Contessa Cookbook".