First, start by browning the butter. Add unsalted butter into a saucepan over a medium heat and bring it to a boil, giving it a stir every so often. Let the butter continue to boil until it beings to foam.2
Give the butter a final stir to release any of the milk solids stuck to the bottom of the pan and strain into a mixing bowl or container through a fine mesh sieve. Place into the fridge to set firm to the consistency of room temperature butter.
Sift flour, baking powder and bicarbonate of soda into a mixing bowl and set aside.
With an electric whisk or a stand mixer fitted with a paddle attachment, cream together the cooled browned butter, light brown sugar, caster sugar and egg until pale and fluffy. Scraping the the bowl a couple times in-between.
Add half the dry ingredients to the creamed butter mixture and gentle fold in. Once the flour and completely incorporated, add in the remainder and mix until it just comes together.
Next, fold in the chopped hazelnuts3 and chocolate chips until evenly distributed through the cookie dough.
Either with an ice cream scoop or by hand portion the cookie dough into 50-75g balls and set onto a baking tray lined with greaseproof paper, then into the fridge for 30-60 minutes to set firm.
In the mean time, preheat the oven to 160℃ (320℉).
Onto pre-lined baking trays separate the cookies leaving plenty of space between them, and into the oven for 10 minutes.
Leave to cool for 5-10 minutes before transferring to a wire rack to cool completely before enjoying!
