Spray non stick cooking spray in bowl. Use a paper towel to evenly spread the liquid and soak up any excess. Set bowl aside for later.
In your second bowl add 1/2 tsp coconut oil and heat in microwave for 15 seconds or until melted. Add 1 TBSP almond coconut milk and an egg yolk. Whisk with fork.
Add 4 TBSP fudge brownie mix and stir. I like to add 2 TBSP at a time to ensure the batter is super smooth. Use your spatula to scrape off the corners where the brownie mix tends to stick.
Transfer cake batter into bowl coated with nonstick spray and microwave for 45 seconds. Rinse spatula, fork and second bowl while the cake is cooking to prepare for the frosting.
Remove cake from microwave and set aside to cool. Add 1 tsp butter to clean bowl. If you’re using a stick of butter 1 tsp would be 1/3 of a tablespoon slice. Heat in microwave for 10 seconds or until creamy when stirred.