Add all ingredients except blueberries into an oversized mug. Stir with a whisk and mix until most of lumps are gone and only very tiny Bisquick lumps remain. Drop in blueberries. Cook in microwave for approximately 1 1/2 -2 minutes. Cake may still have a wet outside, but this is normal. If inside of cake is done (insert a knife to check), then cake is done.