Begin by creaming the butters and sugars for the cookies. Beat in the egg and vanilla.
In a small bowl mix together your flour, baking soda, baking powder, and salt. Mix into the creamed butter and sugars.
Mix in the oats and stir until combined.
Drop teaspoonfuls (or use a small cookie scoop) of dough onto a parchment lined baking sheet. Make a criss cross with a fork to flatten the cookies.
Bake for 10 minutes and allow to cool.
When cookies are completely cooled, flip half of them over. Spread with a spoonful of Nutella (how much you use is totally up to you) and then top with the remaining cookies.