Ingredients:

• For the Chocolate Cake Rounds
• 2 cups (240g) all-purpose flour (see recipe note)
• 1/2 cup (42g) Dutch-process cocoa powder
• 1 teaspoon baking powder
• 1 teaspoon baking soda
• 1/2 teaspoon kosher salt
• 1/4 cup (57g) unsalted butter, room temperature
• 1/4 cup (60ml) vegetable oil
• 1 cup (213g) packed dark brown sugar
• 2 large eggs, room temperature
• 1 teaspoon vanilla extract
• 1 cup (240ml) buttermilk
• For the Filling
• 1 cup (227g) unsalted butter, room temperature
• 1 cup (113g) powdered sugar
• 1 (7 to 7.5-ounce) jar marshmallow creme (about 2 1/4 cups)
• 1 teaspoon vanilla extract