4ouncesunsweetened baking chocolatemelted and cooled slightly
3/4cupplain mashed potatoeswarm*
1 1/2cupspowdered sugar
1 1/2ouncesunsweetened baking chocolatemelted and cooled slightly
2tablespoonsmilk, half-and-half, or heavy cream
To make the cake
Preheat oven to 350 F. Grease and flour a 9x13-inch baking dish. Set aside.
In a medium bowl, whisk together flour, baking soda, and salt. Set aside.
In a large bowl, beat butter and sugar together until combined.
Beat in eggs, buttermilk, and vanilla until well-combined.
Add mashed potatoes and melted chocolate. Mix until incorporated.
Stir in flour mixture until just incorporated.
Pour batter into prepared baking pan, smoothing as needed.
Bake for 35-50 minutes, or until a wooden toothpick inserted in the center comes out clean.
Let cake cool to room temperature before frosting.
To make the frosting
Beat butter and powdered sugar together until well-combined.
Mix in chocolate and milk until completely incorporated.
Spread over cooled cake.
*Instant or regular will work. **The frosting recipe will make enough for a thin layer of frosting. If you like a thicker layer of frosting on your cake, you'll want to double the frosting portion. ***If you prefer a chocolate frosting made with cocoa powder, my chocolate buttercream frosting works well. ****Nutrition facts are estimates.