Preheat the oven to 350°F (175°C). Grease a 9×9-inch baking pan or line it with parchment paper.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large mixing bowl, cream the softened butter and granulated sugar until light and fluffy.
Beat in the eggs one at a time. Add the sour cream, vanilla extract, and cooled brewed coffee. Mix until smooth.
Gradually fold the dry ingredients into the wet mixture until just combined. Avoid overmixing to keep the Mocha Coffee Cake Recipe light and tender.
In a separate bowl, combine the flour, brown sugar, cinnamon, cocoa powder, and cold butter. Mix with a fork or pastry cutter until crumbly.
Spread the batter evenly into the prepared baking pan and sprinkle the streusel topping over the batter.
Bake for 35–40 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool completely.
Whisk together the powdered sugar and brewed coffee until smooth, then drizzle the glaze over the cooled cake before slicing and serving.