45g unsalted butter
3 tbsp packed light brown sugar
3 tbsp whole milk
1/2 teaspoon vanilla extract
40g all-purpose flour
2 tbsp unsweetened cocoa powder
Pinch salt
1 tbsp dark chocolate chips (optional)
Vanilla ice cream, for serving
Place butter in a large, microwave-safe mug. Microwave on high until fully melted, about 1 minutr. Swirl to coat the mug with melted butter, then pour the butter into a small bowl.
Add brown sugar, milk, and vanilla extract, and whisk until smooth. Add all-purpose flour, cocoa powder, salt, and stir until combined. Fold in chocolate chips if desired.
Scrape the batter back into the mug. Microwave on high for 1 minute and 30 seconds. The brownie is ready when the center is slightly gooey and the edges bounce back when pressed. If not ready, microwave for 15 seconds more. Top with ice cream and enjoy!