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One tablespoon of butter

Soften for about 10 seconds in the microwave

Stir in 2 Tablespoons of sugar

Now add in some egg, it can be a whole egg or only part. (this step is optional but the cake won't be as fluffy)

Add in an estimation of vanilla, only a few drops

Now add 2 tablespoons of sour cream

And 1/4 cup flour

And 1/8 teaspoon baking powder

Now for the crumb topping.. In different mug start with 1 tablespoon butter

Add in 2 tablespoons flour

1 tablespoon brown sugar

And 1 teaspoon cinnamon

Mash together with fingers of fork

And add to top of your original mug

Now it's ready for the microwave! Microwave for about 1 minute if not done out back in for 10 seconds

And eat!

Enjoy!