Mix Wet Ingredients: In a microwave-safe mug or bowl, combine the vegan milk, maple syrup, and peanut butter. Stir well until the peanut butter is fully incorporated.
Add Dry Ingredients: Stir in the oat flour and baking powder until everything is well-combined and smooth.
Microwave: Place the mug or bowl in the microwave and cook on high for 1½ to 2 minutes. The cake should puff up and look firm on top. If needed, microwave in 10-second intervals until done.
Cool & Enjoy: Let the cake cool for a minute or so before digging in. You can eat it straight from the mug!
Notes
After the oatmeal mug cake is done cooking in the microwave, let it rest for a couple of minutes before enjoying.
Add any toppings of your choosing. I went with chocolate chips, sliced almonds, and a drizzle of maple syrup.
If your peanut butter is hard or cold, soften by warming it up in the microwave for about 30 minutes. This will make it easier to mix with the rest of the wet ingredients.