Step 1

Special equipment: a 12-ounce microwave-safe ceramic mug and a microwave oven

Step 2

Put the flour, sugar, cocoa powder, baking powder and salt if using in a 12-ounce microwave-safe ceramic mug. Blend thoroughly with a fork. Add the milk, vegetable oil and vanilla if using and blend until smooth. Stir in the chocolate chips.

Step 3

Microwave on high for 90 seconds. Do not overcook or the cake will be dry. Let cool for 2 to 3 minutes before eating.