Copy and paste from the following website.
http://www.yummly.com/recipe/external/Chocolate-and-Peanut-Butter-Mug-Cake-1121585
| Unsalted butter | 2 tbsp |
| Dark chocolate | 40 g |
| Egg | 1 |
| Milk | 2 tbsp |
| Sugar | 3 tbsp |
| Salt | some |
| Flour | 3 tbsp |
| Baking powder | 1/4 tsp |
| Peanut butter | 1 tbsp |
| Coarsely chopped peanuts | 1 tbsp, optional |
Add the butter and chocolate to a large microwave-safe mug and microwave in short 20-second bursts until melted.
Add the egg and milk and beat with a fork until smooth.
Add the sugar, salt and flour and beat again to smooth, microwave for 30 seconds then gently add the peanut butter to the top of the batter - do not stir.
Microwave again for around 1 minute to 1 minute 10 seconds, or until cooked.
(optional) top with more peanut butter or with peanut butter and peanut sprinkled on top.
If you want a more chocolate-y flavor, remove 1 tbsp of flour and add 1 tbsp of unsweetened cocoa powder.
Again, to add more depth of flavor, add a pinch of instant espresso powder. If doesn't add a coffee flavor, just gives the chocolate flavor an incredible depth.
