In a large mixing bowl, cream the butter, brown sugar, and coconut sugar. Then, beat in the vanilla, orange juice, egg, and egg yolk. Next, beat in the cinnamon, baking soda, salt, and gluten free flour blend. Finally, stir in the oats. Cover and store in the fridge for at least 30 minutes.
Preheat the oven to 350 degrees.
Scoop 1 1/2 inch balls onto a lined baking sheet. Then, bake for 8-10 minutes, until golden brown. Allow to cool for a few minutes before removing from the sheet pan.
VANILLA DRIZZLE: In a small bowl, melt the butter. Then, whisk in the vanilla and 1 Tbsp. of milk. Next, whisk in the powdered sugar. Add more sugar or liquid until desired consistency is reached. You want it to be pourable (drizzle-able), but also thick! Use a spoon to drizzle over the cookies.