Add the margarine/butter and the sugar to a mug or ramekin dish. Use one that's around 3.5-inches wide (all the way down) to ensure even cooking. Baking time may vary if you use a different size.

Mix the margarine and sugar together until smooth, then stir in the vanilla extract.

Add the flour and the plant-based milk. Mix well until you have a smooth, slightly thick cake batter. Use a teaspoon to smooth the top out evenly.

Add the sprinkles to the top of the batter if using.

Bake in the microwave for 50seconds to 105 seconds (please see notes for the correct baking time for your microwave).

Let the cake stand at room temperature for a few minutes then enjoy!