Preheat the oven to 325º F. Butter or spray a 9x13 inch pan.
Combine all of the ingredients for the topping in a mixing bowl. Use your hands or spatula to combine the mixture into a clump-able sandy like texture. Set aside.
In a separate mixing bowl, beat the butter, brown sugar and sugar with electric mixer for 1-2 minutes, until fluffy. Beat in the eggs and vanilla. Use a spatula to hand mix in the brewed espresso.
Add the flour, baking powder, salt, and finely ground espresso beans, mixing with a spatula until just combined. Just combined means it's okay if the batter has flour lumps or minimal streaks of flour visible. Pour the batter into the pan. Sprinkle the topping evenly over the batter, breaking up large clumps of topping with your fingers.
Bake for 50-55 minutes or until the topping is golden brown and a toothpick inserted in the center comes out clean.