Choose your mug: Use a microwave-safe mug that holds at least 12 ounces to avoid overflow.
Mix dry ingredients: Add protein powder, cocoa, sweetener, baking powder, and salt. Stir to break up any clumps.
Add wet ingredients: Pour in milk, oil (or nut butter), and vanilla.
Stir until smooth and thick, like brownie batter. If it’s too dry, add 1–2 teaspoons more milk.
Fold in extras: Stir in chocolate chips or a few nuts if using.
Microwave: Cook on high for 40–60 seconds. The top should look set but still slightly glossy in the center.
If needed, add 10-second bursts until done. Avoid overcooking.
Rest and serve: Let it sit for 30–60 seconds to finish setting. Enjoy as is, or top with a spoon of yogurt, a drizzle of nut butter, or berries.