- 1 1/2 cups all-purpose flour
- 1/2 cup packed brown sugar
- 1 teaspoon baking powder
- 1 teaspoon baking soda
- 1/4 teaspoon salt
- 1 cup chunky peanut butter
- 3/4 cup sour cream
- 3 tablespoons butter, melted
- 2 tablespoons boiling water
- 1 cup semisweet chocolate chips
- 1 serving cooking spray
- 3/4 cup whole milk, warmed
- 3/4 cup white sugar
- 6 tablespoons unsweetened cocoa powder
- 1 teaspoon vanilla extract
- Whisk flour, brown sugar, baking powder, baking soda, and salt together in a small bowl.
- Whisk peanut butter, sour cream, butter, and boiling water in a large bowl until thick. Stir flour mixture into peanut butter mixture until batter is well mixed; fold in chocolate chips.
- Generously coat liner of a 6-quart oval slow cooker with cooking spray. Spread batter evenly in slow cooker.
- Whisk milk, white sugar, cocoa powder, and vanilla extract in a small bowl until smooth. Pour over batter.
- Cook on High until sides of cake begin to pull away from liner and appear solid (the center will still be soft), 1 1/2 to 2 hours.