Melt butter in microwavable mug or ramekin.
Add egg yolk and dash of vanilla, then mix with fork.
Add both sugars, mix well with fork.
Add gluten free flour (or regular if you choose), baking soda, and salt. Mix with fork to fully combine.
Fold in 1 tablespoon of chocolate chips.
Microwave for 30-40 seconds or until just set (don’t overcook!)
Dig in or top with a little vanilla ice cream.