- 1/4 cup sugar
- 3 packed tablespoons dark brown sugar
- 1/2 cup walnuts, toasted and coarsely chopped
- 2 teaspoon vanilla extract
- 1/2 teaspoon ground cinnamon
- 2 cups unbleached all-purpose flour
- 1 teaspoon baking soda
- 1/2 teaspoon fine salt
- Generous pinch freshly grated nutmeg
- Generous pinch ground mace
- 3/4 cup unsalted butter, plus more for the pan, room temperature
- 1 cup sugar
- 2 large eggs, room temperature
- 1 cup sour cream
- 1 1/2 teaspoons vanilla extract
Make the streusel by mixing the sugar, brown sugar, walnuts, vanilla, and cinnamon together in a small bowl. Set it aside.
Preheat the oven to 350 degrees F. Generously brush a round 9 by 2-inch deep cake pan with butter. In a medium bowl whisk the flour, baking soda, salt, nutmeg and mace together and set it aside.
In a standing mixer fitted with the paddle attachment, or with an electric hand-held mixer, cream the butter and sugar on medium speed until light and fluffy. Add the eggs, one at a time, mixing until incorporated. Mix the vanilla with the sour cream. Add the flour mixture in 3 parts to the butter mixture, alternating with the sour cream in 2 parts until just combined.