Adapted from Instructables.com
1/4 cup flour
1/4 cup packed brown sugar
2 Tbsp unsweetened cocoa powder
2 Tbsp canola or other mild vegetable oil
2 Tbsp milk, coffee or water
In a heatproof mug or ramekin, stir together the dry ingredients until no lumps remain. Stir in the oil and milk until you have a thick paste.
Microwave on high for a minute, checking it after 30 seconds (microwaves vary) – it will be done when it’s springy on top but still a bit gooey – like the very best brownie. Eat warm.