Coffee Mug Cake

Ingredients (9)

• + 1 tablespoon butter, softened add to pantry
• + 2 tablespoons white sugar add to pantry
• + ½ beaten egg add to pantry
• + 2 tablespoons sour cream add to pantry
• ✓ 2 drops vanilla extract, or more to taste
• + ¼ cup all-purpose flour add to pantry
• + ⅛ teaspoon baking powder add to pantry
• + 1 tablespoon brown sugar add to pantry
• + 1 teaspoon cinnamon add to pantry