Combine the cake flour, hot chocolate mix, cocoa powder, & baking powder in a small bowl. Then, add egg, milk, & olive oil to the dry ingredients.
Warm butter in a microwave-safe mug or two ramekins until melted.
Pour half of the batter into the prepared mug & top it with marshmallow creme or mini marshmallows. Finish it with the rest of the batter.
Wipe down the sides of the mug & microwave for 1 minute. Continue cooking for 30 seconds at a time.
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