2 1/4 cups all purpose flour
1/2 cup ground walnuts
1 teaspoon baking powder
1 teaspoon salt
2 sticks plus 2 teaspoons unsalted butter, room temperature
3 ounces bittersweet chocolate
1/4 cup coffee
1 teaspoon espresso powder
1 3/4 cups sugar
4 large eggs, room temperature
2 teaspoons vanilla extract
1 cup milk, room temperature
Directions:
Preheat oven to 350 degrees F. Butter a 9 to 10 inch bundt pan, dust inside with flour, and tap out the excess.
Whisk flour, ground walnuts, baking powder, and salt together in a medium bowl.
Combine 2 tablespoons butter, chocolate, coffee, and espresso powder in a metal bowl. Place over a pot of simmering water and stir until melted and combined. Remove from heat.
Combine remaining 2 sticks of butter and sugar in a stand mixer and beat with paddle attachment on medium speed for about 3 minutes until smooth and creamy.
Add in eggs one at a time, beating well after each addition.
Add in vanilla extract.
Add in flour mixture and milk in five alternating additions, starting and ending with the flour mixture. Mix on low speed after each addition just until combined.
Scrape just under half of the batter into the bowl with the melted chocolate and fold gently to combine.
Pour the vanilla batter into the bottom of the bundt pan. Pour the chocolate batter on top. Use a knife to lightly marble the batter.
Bake for 65-70 minutes until a thin knife inserted in the center comes out clean. Cool on wire rack for about 10 minutes before un-molding.