Add all of the ingredients for the cake to a mixing bowl, and blend until smooth.
Evenly separate the batter into two well greased small mugs.
Microwave for 1 ½ - 2 minutes, or until the cakes are cooked through.
If using the frosting, place the hot fudge sauce and peanut butter into a microwave safe bowl, and heat for about 20 seconds. Stir to combine, and add the frosting to the top of the cakes before serving.
Notes
Nutritional data is without the optional frosting. See below for data with frosting:
Use good quality ingredients like creamy peanut butter and pure vanilla extract for enhanced flavor.Don't over-mix the batter. This can result in a dense and rubbery texture. Just mix until all ingredients are well incorporated.Microwaving time can vary depending on your microwave's wattage. Start with 1 minute and increase by 15-second intervals until fully cooked. The cake should be moist but not gooey in the center.