Chocoflan

Name: Chocoflan
Ingredients: 0.5 c. (1 stick) plus 2 tbsp. unsalted butter, softened; 0.25 c. homemade or store-bought caramel sauce; 1 c. (215 g.) lightly packed dark brown sugar; 1 large egg, room temperature; 1.5 c. (180 g.) all-purpose flour; 0.25 c. unsweetened Dutch-processed cocoa powder; 1 tsp. baking powder; 0.75 tsp. baking soda; 0.5 tsp. kosher salt; 0.5 c. (120 ml.) brewed coffee or water, room temperature; 0.5 c. (120 ml.) buttermilk, room temperature