Sour Cream Coffee Cake (with a Chocolate Cinnamon Swirl

Ingredients:

For the crumb topping:

3/4 cup all-purpose flour
3/4 cup firmly packed dark brown sugar
1/2 teaspoon salt
3/4 cup pecans, toasted

[Let them cool before proceeding.]

6 tablespoons unsalted butter, cold, cut into 1-inch cubes

For the chocolate cinnamon swirl:

1/2 cup sugar
1 teaspoon dark unsweetened cocoa powder
1 teaspoon cinnamon

For the sour cream cake:

3 1/2 cups all-purpose flour
1 teaspoon baking powder
1 1/2 teaspoons baking soda
1/2 teaspoon salt
1 cup (2 sticks) unsalted butter, soft but cool, cut into 1-inch pieces
2 1/4 cups sugar
4 large eggs
16 ounces sour cream
1 1/2 teaspoons pure vanilla extract

1. First make the crumb topping by putting the flour, sugar and salt in a food processor, pulsing for 5 seconds to mix. Add the pecans and pulse until the pecans are finely chopped and thoroughly incorporated. Add the butter and pulse until combined……it’ll look like coarse sand. Cover with plastic wrap and store in the refrigerator.
2. To make the chocolate cinnamon swirl, simply whisk together the sugar, cocoa powder and cinnamon in a small bowl and set aside.
3. Preheat the oven to 350 degrees & butter a 9 X 13-inch baking pan. Sift the flour, baking powder, baking soda and salt together into a medium bowl.
4. In the bowl of an electric mixer fitted with the paddle attachment, cream the butter until smooth and ribbonlike. Scrape down the bowl and add the sugar. Beat until the mixture is smooth and starts to look fluffy.Add the eggs, one at a time, beating well after each addition. Scrape down the bowl and mix again for 30 seconds.
5. Add the sour cream and vanilla and beat just until incorporated.Add the dry ingredients in three additions, scraping down the bowl before each addition and beating only until each addition is just incorporated. Do not over mix.
6. Pour one third of the cake batter into the prepared pan. Use an offset spatula to spread the batter evenly.
7. Sprinkle half the chocolate cinnamon swirl mixture over the batter, covering the entire surface of the batter.Spoon half of the remaining batter over the swirl mixture–do this in blobs, as Matt suggested–and spread it evenly. Top with the remaining swirl mixture, then the remaining batter, and spread the batter evenly. Sprinkle the crumb topping evenly over the top of the batter.
8. Bake in the center of the oven, rotating the pan three times during baking, for 1 hour, or until a toothpick inserted in the center of the cake comes out clean. Let the cake cool in the pan on a wire rack for 30 minutes, then serve.