In a large bowl, cream butter, brown sugar, and granulated sugar together. Add egg, tahini, and vanilla and mix until well combined.
In a medium bowl, combine oats, oat flour, baking powder, cinnamon and salt.
Add ½ of your dry ingredients to your wet mixture until well combined. Mix in the last half until just combined.
Fold in chopped chocolate chips.
Scoop cookies into a parchment lined baking sheet and top with dark chocolate chips.
Bake in 375°F oven for 10-14 minutes or until edges just begin to crisp.
Allow to cool for 5-10 minutes before enjoying!