1. For the prep:

2. Spray an 8-inch round baking pan generously with baking spray and line the bottom with a round piece of parchment paper. Spray the paper lightly with baking spray. Set pan aside. Tear a piece of heavy-duty foil large enough to wrap around the outside of the pan. (you can also use a double thickness of regular foil). Set aside until baking time.

3. For the batter:

4. In a medium-size microwave-safe bowl, cream together the butter and sugar with a spatula until sugar is completely incorporated.

5. Add the egg and mix well.

6. Sprinkle the baking powder, baking soda and salt over the butter mixture and stir to combine.

7. Add ⅓ of the flour (approximately, this does not have to be precise) and stir till flour is almost completely incorporated. It’s fine if there is still a bit of flour remaining. Add ½ (again, approximately) of the buttermilk and stir until buttermilk is pretty much incorporated. Repeat with flour and buttermilk alternatively. You will start and end with the flour. Add vanilla and stir well one more time.

8. Spread evenly into the prepared baking pan.
9. Cover, and refrigerate overnight.

10. For the crumb topping:

11. Wash out the mixing bowl. Place butter in the bowl and heat on high power for 25-30 seconds or until butter is partially melted. You want about half of the butter melted. Every microwave is different so check it after 25 seconds. Add the remaining crumble ingredients and stir with a fork until large crumbs form. Cover and refrigerate overnight.

12. To finish:

13. The next morning, preheat the oven to 350˚F. Bake the cake for 25 minutes, then carefully remove from the oven and, using your hands, gently top with the crumble mixture (don’t press it in at all, just sprinkle the topping over the top of the cake), mounding it up a bit in the center. If the crumb mixture has formed large clumps, just break them up with your fingers as you sprinkle the mixture over the cake.

14. Before returning to the oven, wrap the outside of the pan with the foil (this will prevent the cake from turning too brown on the edges as it continues to bake).

15. Return coffee cake to the oven and bake for another 10-20 minutes, or until a toothpick inserted in the center comes out clean. Remove from oven and allow to cool for 10 minutes.

16. After 10 minutes, invert coffee cafe and turn out onto a large dinner plate. Invert again onto a cool rack so that crumb side will face up and allow to cool for at least 15 minutes before serving.

17. Serve as is or sprinkle lightly with powdered sugar. For a special treat, drizzle with Vanilla Bean Drizzle.

For the drizzle (optional):

1. Combine 1 cup powdered sugar with 2 tablespoons of milk or half and half. Stir with a fork until smooth. Add a bit more half and half (or milk) to thin, a few drops at a time until you have a thick but drizzle-able icing. Add the vanilla beans scraped from ½ of a vanilla bean pod or ½ teaspoon vanilla bean paste. Drizzle in thin ribbons over the crumble layer.