Preheat the oven to 350° F. Line a cookie sheet with parchment paper or a silicone baking mat.
Cream together the butter, brown sugar and granulated sugar until light in color and fluffy in texture.
Add the egg and canola oil. Mix until combined.
Add the flour, rolled oats, cornstarch, baking soda and salt. Mix until a soft dough forms.
Add in the chocolate chips and mix until evenly distributed.
Portion out the cookie dough into 1/3 cup portions. Roll into a ball and then flatten slightly before baking.
Bake at 350° F for 11-13 min or until the edges start to turn golden brown.
Allow the cookies to cool on the pan. Once almost cooled, spread 1-2 tbsp of cookie butter onto each cookie.
Top with come biscoff cookie crumbs, if desired.
Enjoy!