Preheat & Prep:Preheat oven to 350°F (175°C). Grease and flour your cake pan or line it with parchment paper.
Combine Dry Ingredients:In a large mixing bowl, whisk together the cake mix and instant pudding mix until evenly combined.
Mix Wet Ingredients:In a separate bowl, whisk eggs, vanilla, vegetable oil, sour cream (or buttermilk), and cooled coffee until smooth.
Create Batter:Slowly pour the wet ingredients into the dry mixture. Stir gently until just combined. Avoid overmixing.
Add Chocolate Chips:Fold in the Nestlé Toll House chocolate chips for melty bursts of chocolate.
Bake:Pour the batter into the prepared pan and bake for 45 minutes, or until a toothpick inserted in the center comes out clean.
Cool:Let the cake cool in the pan for 10 minutes before transferring it to a wire rack or serving plate.
Prepare Ganache Frosting:In a small saucepan over low heat, melt the butter. Whisk in cocoa powder, powdered sugar, vanilla extract, and milk until smooth and glossy. Stir in walnuts if desired.
Frost the Cake:Pour the warm ganache over the cooled cake and spread evenly with a spatula.
Serve:Enjoy immediately for a gooey treat or reheat slices gently before serving for warm indulgence.
