(If using an oven, preheat to 330 F.) Combine batter dry ingredients and mix well. Add wet and mix until just mixed. In a tiny bowl, combine all streusel ingredients. Fill a greased muffin tin 1/2 way with the batter (or a ramekin or mug, if using the microwave). Sprinkle on two-thirds of the streusel, then spoon the remaining batter on top. Finally, sprinkle on the rest of the streusel. Cook 12-13 minutes in the oven, or around 1 minute in the microwave. (Microwave times may vary.)View Mug Cake Nutrition Facts