In a large microwave-safe mug or bowl, combine the protein powder, almond flour, cocoa powder, baking powder, and salt. Stir until well mixed.
Add the almond milk, maple syrup, and almond butter to the dry ingredients. Mix until you have a smooth batter. If desired, fold in chocolate chips or nuts.
Microwave the mixture on high for 60 seconds. Keep an eye on it to prevent overflowing; if it's not fully firmed up, give it an additional 10-15 seconds.
Once cooked, let the brownie cool for a minute. You can enjoy it directly from the mug or transfer it to a plate for a fancier presentation.
Optional: Dust with powdered sugar or drizzle with a bit more almond butter for an extra touch of sweetness and visual appeal.
Notes
Optional toppings include powdered sugar or extra almond butter.