For the streusal

1. In a medium-sized bowl, combine the dry ingredients (flour, sugar and cinnamon). Whisk to combine. Next add the melted butter until it’s well combined. The mixture might be crumbly but stick together when pressed between your fingers. Then fold in the chopped nuts and chocolate chips.

For the cake

1. Preheat oven to 350°F. Grease two 9-inch loaf pans, and line with parchment paper. Set aside.
2. Cream room temperature butter and sugar together in a stand mixer until light and fluffy, about 3-4 minutes.
3. Next add the eggs and vanilla extract and beat until well incorporated, scrape down the sides of the bowl as needed. Add the sour cream and beat until well incorporated.
4. In a separate bowl, combine remaining dry ingredients. Slowly add the dry ingredients and beat at a low speed just until flour is mixed. Turn off your mixer and use a spatula and mix by hand until well combined.
5. Pour 1 1/2 cup of the batter into the bottom of each of the pans and spread evenly. Then sprinkle 1/2 cup of the streusel over the batter in each pan. Divide remaining batter evenly between the two pans and top with remaining streusel, half on each loaf.
6. Bake at 350°F for 55-60 minutes. Check the coffee cake for doneness by inserting a toothpick into the center of the cake. If the toothpick comes out clean, then the cake is done. Allow to cool completely.