single serve chocolate chip cookie in a mug! melt a tablespoon of butter in a mug & add a tbsp of white sugar and a tbsp of brown sugar. add a few drops of vanilla, a pinch of salt and mix. add an egg yolk and stir again. it will look soupy. add a 1/4 cup of flour and mix. It will start to look like cookie dough. add 2 tbsps of chocolate chips, give a final stir, and put in the microwave for 40-60 seconds, and your done!