- Preheat your oven to 350°F. Lightly spray three 8-inch cake pans with non-stick spray and line the bottoms with parchment paper.
- In a medium bowl, whisk the flour, cocoa powder, baking soda, and salt.
- Add the butter and 12 ounces chocolate to a large bowl. Melt over a double boiler or in the microwave in 15-second intervals until smooth. Allow to cool slightly, then whisk in the brown sugar and vanilla extract until well combined.
- Add the room temperature eggs one at a time and mix until just combined after each.
- Gently mix in about half of the dry ingredients until just combined. Stir in the coffee (or milk) and sour cream, then add the rest of the dry ingredients. Mix until just combined and the batter is smooth. Fold the remaining 4 ounces chopped chocolate or chocolate chips into the batter.
- Bake: Divide the batter evenly between the three prepared cake pans. Bake for 20-22 minutes. A toothpick should come out mostly clean but with a few cakey crumbs attached.
- Allow the cake layers to cool completely in the pan, then transfer to the fridge or freezer to chill before frosting the cake. To make frosting the cake easier, wrap the individual cake layers in plastic wrap and freeze overnight (and up to 2 months) before frosting.
Source: https://www.mealsbymolly.com/chocolate-brownie-cake