Preheat the oven to 350F . Spray or line 8muffin cups.

In a large bowl, combine all-purpose flour, sugar, hot cocoa mix, baking powder, and salt. Set aside.

In another large bowl, whisk together egg, vanilla, milk, melted butter ( cooled) and sourdough starter.

Fold the egg mixture into the flour mixture with a rubber spatula.

Fold in chocolate chips into the dough .

Transfer to dough to prepared muffin tin.

Bake for 12-13 minutes, or until a toothpick inserted in the center of one of the muffins comes out clean.

Then add marshmallows to the muffins and continue to bake for another 2 minutes.

Leave to cool in the muffin tin for 5 to 10 minutes before removing from tin and transferring to a wire rack to cool completely.