Instructions

1. 1

   Preheat oven to 350 degree F and place a rack in the center of oven. Coat inside of the pan with melted butter using a pastry brush or paper towel.

2. 2

   Sprinkle the sides and center of pan with turbinado sugar.

3. 3

   Toast walnuts in the oven for 7 to 8 minutes, stirring often until the nuts are light golden.

4. 4

   Remove from oven and cool on rack.

5. 5

   Sift the flour, cocoa powder, and baking soda over a bowl.

6. 6

   Add brown sugar, salt, and nutmeg, and toss to blend completely.

7. 7

   Add the walnuts and bittersweet chocolate chunks and stir to blend thoroughly.

8. 8

   In a bowl of electric stand mixer, blend thoroughly buttermilk, sour cream, vanilla, and chocolate extract (if using) with a paddle attachment.

9. 9

   Add the flour mixture in 4 stages, blending well after each addition. Stop often to scrape down the sides and bottom of the bowl with a rubber spatula.

10. 10

    Transfer the batter to the prepared pan, then use a rubber spatula to smooth and even the top.

11. 11

    Bake for 35 to 38 minutes, until a cake tester inserted in the center of the cake comes out clean.

12. 12

    Remove the pan from the oven and cool on a rack for 20 minutes. Invert the pan onto the rack and lift the pan off the cake.

13. 13

    Let the cake cool completely on the rack.

14. 14

    Serve the cake at room temperature.