First, brown the butter. Put the butter in a small saucepan over a high heat. Cook until the butter melts, bubbles up, then dissipates and begins to turn golden brown at the bottom of the pot.
Pour into a bowl and allow to solidify at room temperature.
Once set, preheat the oven to 180 C (350 F) and line a few trays with baking paper.
Using a stand mixer fitted with paddle attachment, beat the browned butter and both sugars until light and fluffy.
Beat in the eggs one at a time until combined, then the vanilla extract.
Add the flour, cornstarch, baking soda, baking powder and salt and beat on a low speed until just incorporated.
Fold in the chocolate chips and Nutella.
Use a medium cookie scoop to drop balls of dough onto the lined baking trays and optionally sprinkle with sea salt.
Bake for 9 minutes, until lightly golden around the edges. Allow to cool on trays.
Makes 25 cookies.
Happy baking!
Recipe by Butter Baking at https://www.butterbaking.com/2015/06/09/chocolate-chip-nutella-swirl-cookies/