Take a ceramic mug. Coat the inside of the mug with butter using a brush. Add 3 tbsp of all-purpose flour, 3 tbsp of powdered sugar, 2 tbsp of unsweetened cocoa powder, a little less than ¼ tsp of baking powder, and a pinch of salt. Mix everything well using a fork.
Then add other ingredients, 1 egg, 2 tbsp of milk, 4-5 drops of chocolate essence. Stir it until smooth. If you want, you can add chocolate chips, nuts, or raisins as per your taste and choice.
Keep it in the microwave for 1 minute. Let it sit for a while or until it cools down and dig inches.