Make a decadent single-serve dessert in a coffee cup in the microwave. It's so easy and only takes a few minutes!
Melt the butter in a coffee mug.
Add water, vanilla and salt and stir until smooth.
Add sugar, cocoa powder and flour and stir until all the lumps are out. Add the peanut butter in one clump in the center of the mug and only stir it in a little bit. You want a big, melty tunnel of peanut butter in the center once it's done.
Cook in the microwave for 30-40 seconds. If you want less "lava" and more cake you can cook it for 10 seconds more.
You may have to adjust the cooking time since all microwaves cook at different speeds. Cook in 15 second intervals until the desired consistency is reached.