- 2 tablespoons all-purpose flour
- 2 tablespoons brown sugar
- 2 tablespoons unsweetened cocoa powder
- 1/8 teaspoon baking powder
- 1/8 teaspoon instant coffee powder (optional)
- 1 pinch salt
- 2 tablespoons vegetable oil
- 2 tablespoons water, or as needed
- 2 drops vanilla extract
- Combine flour, sugar, cocoa powder, baking powder, instant coffee, and salt in a microwave-safe mug or small bowl. Mix in vegetable oil, water, and vanilla extract until mixture is smooth and glossy. Add more water, 1/4 teaspoon at a time, if mixture looks a little dry.
- Microwave on high until top looks dry, about 1 minute.