Step 1: Prepare the Bundt Pan. Preheat your oven to 350°F (175°C). Grease your Bundt pan thoroughly with butter or a non-stick spray.
Step 2: Cream Butter and Cream Cheese. In a large mixing bowl, beat together the softened unsalted butter and cream cheese until light and fluffy.
Step 3: Add Sugars and Eggs. Gradually add in the light brown sugar and granulated sugar, mixing until well combined. Then, add the eggs, one at a time, mixing well after each addition.
Step 4: Combine Dry Ingredients. In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, cornstarch, and salt.
Step 5: Mix Wet and Dry Ingredients. Alternate adding the dry ingredients and buttermilk to the wet mixture, starting and ending with the dry ingredients.
Step 6: Prepare the Chocolate Batter. Scoop out half of the batter into another bowl. To this half, add the cocoa powder and mini chocolate chips, mixing until fully incorporated.
Step 7: Layer the Batter in the Bundt Pan. Spoon the vanilla and chocolate batters into the prepared Bundt pan in alternating layers. Use a knife or skewer to gently swirl the two batters together.
Step 8: Bake. Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Step 9: Prepare the Ganache (Optional). Heat the heavy cream in a small saucepan until it begins to simmer. Remove from heat and add the chocolate chips, stirring until melted and smooth.
