Ingredients

Crumb Topping

1/3 cup packed dark brown sugar
1/3 cup granulated sugar
1/3 cup flour
1/4 to 1/2 tsp. cinnamon
1/8 tsp. cardamom
4 Tbsp. unsalted butter cold and cut into 1/2 inch chunks
1 cup toasted nuts chopped; i.e. walnuts, pecans or almonds

Cake

3 cups flour
1 Tbsp. baking powder
1 tsp. baking soda
1 tsp. ground cinnamon
1/4 tsp. ground cardamon
1/4 tsp. salt
1 3/4 cups sour cream
1 cup packed dark brown sugar
1 cup granulated sugar
3 eggs
7 Tbsp. unsalted butter (browned)

Instructions

To make the Crumb Topping:
Combine the sugars, flour, cardamom, cinnamon and butter together until the mixture resembles coarse meal.
If you have a few pea sized lumps of butter, that's fine.
Stir in the walnuts and set aside.

For the Cake:
Spray two 9 inch springform pans, or two large 6-cup cupcake tins with cooking spray (I use pan release), and set aside.
In a small saucepan, melt the butter over medium high heat. Cook the butter until it turns a golden brown and develops a nutty aroma.
You will notice that the milk solids will float to bottom of the pan and will turn dark brown/black which is what you are looking for!
Take the butter off the heat and set aside to cool.

In a medium bowl combine the flour, baking powder, baking soda, cinnamon, cardamom and salt together.

In a large bowl, combine the sour cream, sugars, eggs and browned butter together.
Stir the dry ingredients into the sour cream mixture, mixing just until all the ingredients are thoroughly combined. You don't want to mix it too much!
Sprinkle the crumb topping over both cakes, wrap in plastic wrap and refrigerate overnight if desired.

To Bake Cakes:
Pre heat oven to 350 degrees.
Bake refrigerated cakes for 35 - 40 minutes or until the tops are golden brown and a cake tester inserted into the center comes out with moist crumbs attached.
For cakes that aren't refrigerated, bake for approximately 25 minutes.
These cakes can also be frozen - to bake frozen cakes, unwrap from the freezer and bake for 45 minutes.