Preheat your oven to 350°F (175°C) and prepare an 8x8 baking dish by greasing it lightly.
Prepare the Crumble Mixture: In a mixing bowl, combine ⅔ cup yellow cake mix, 1 cup brown sugar, chopped pecans, melted butter, 1 tsp cinnamon, and ½ tsp espresso powder. Mix these ingredients together until they form a delightful crumble. Set the bowl aside.
Prepare the Batter: In another bowl, combine the remaining yellow cake mix, 1 & ½ cups sour cream, and 3 eggs. Mix these ingredients vigorously until you achieve a smooth and creamy batter.
Layer the Goodness: Spray or grease the prepared baking dish to prevent sticking. Begin by layering the components in the following order:
Bake to Perfection: Place the baking dish in the preheated oven and bake for approximately 40-50 minutes. The coffee cake is done when a toothpick inserted into the center comes out clean or with just a few crumbs clinging to it.
Let it Rest: Once baked, remove the coffee cake from the oven and let it cool in the baking dish for about 10-15 minutes. This will allow the flavors to settle and the cake to set.
Serve and Enjoy: Cut the coffee cake into slices and serve it warm or at room temperature. It pairs beautifully with a steaming cup of coffee or your favorite beverage.
