Preheat the oven to 350°F.
Grease your angel food cake pan.
In a large bowl, cream the softened butter and sugar until light.
½ cup butter, 1 cup granulated sugar
Add the eggs one at a time, beating after each one. Add in the vanilla extract and sour cream. Mix well.
2 eggs, 1 teaspoon vanilla extract, 1 cup sour cream
In a separate bowl, combine the flour, baking soda, baking powder, salt, and cinnamon.
2 cups all-purpose flour, 1 teaspoon baking powder, 1 teaspoon baking soda, ½ teaspoon salt, 1 teaspoon ground cinnamon
With your mixer on low, slowly add the flour mixture to the wet ingredients. Mix until all ingredients are combined, scraping down the sides with a spatula.
To make the streusel, combine brown sugar, cinnamon, and chopped walnuts in a separate bowl.
¼ cup brown sugar, 1 ½ teaspoon ground cinnamon, ¾ cup chopped walnuts
Spoon half of the batter into the pan and spread using the back of your spoon.
Sprinkle half of the streusel mix over the batter.
Spoon the rest of the batter into the pan, again spreading it with the back of the spoon.
Top the cake off with the rest of the streusel mix.
Bake at 350°F for 40 minutes, until a cake tester comes out clean.
Let cake cool on wire rack for at least 30 minutes.
Carefully lift the cake out of the pan and place on a plate.
To make the glaze, whisk together the powdered sugar and milk until you have desired consistency. If you prefer a thicker glaze, add ¼ cup powdered sugar more to the mix.
2 tablespoons milk, Add ¼ cup powdered sugar to make it a thicker glaze, 1 cup powdered sugar
Drizzle the glaze over the cake using a bag or spoon.