Whisk in the melted butter, brown sugar, vanilla and egg until no streaks of yellow from the eggs are left.
Add the dry ingredients including, oat flour, baking soda and salt to the wet ingredients and stir with a rubber spatula until combined.
Fold in the chocolate chips. Cover the dough and chill it in the fridge for at least 1 hour or up to 3 days.
Scoop the chilled cookie dough out onto a baking sheet using a medium cookie scoop, or a heaping tablespoon, land bake in the pre-heated oven for 8-10 minutes.