In a microwaveable mug put candies and 3 tbsp of milk (saving 1 tbsp for later). Microwave for about 20 seconds. Careful to not microwave too long or else milk will spill over. Stir chocolates in milk with fork to dissolve. Chocolate should melt, though may appear gritty. Microwave for another 20 seconds. Chocolate should melt further and thicken. Stir again with fork.
Add in flour and baking powder. Stir with a small whisk until batter is smooth. Batter will be quite thick. Add in the remaining 1 tbsp of milk and stir to thin out batter. Add a few additional m&m's (5-6) on top if desired.
Cook in microwave for 1 minute. Surface of cake should be dry.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.