Start by browning the butter. Melt the butter in a wide, heavy-bottomed (and preferably light-coloured) pan over medium-low heat. Stir the butter around the pan to ensure that it melts evenly, following which you will start to see it foaming and sizzling around the edges.
Keep a close eye as the melted butter shifts hues from a lemony-yellow to a golden tannish-brown, before finally getting to the toasty-brown we want. You’ll know you’re there once the kitchen starts filling with a soul-stirringly nutty aroma!
Remember, we want to brown the butter, not burn it. There’s a fine line between the two, given that butter burns at a lower smoke-point than other oils. Use a spoon or rubber spatula to clear away the foam and check on how far the butter has browned. Once some foam starts to subside and you can see dark brown specks at the bottom of the pan, remove the butter from heat and pour out into into a heat-proof bowl to cool.
Next toast the nuts to intensify their flavour: heat in a skillet (over medium heat), stirring occasionally, until they are just about browned and fragrant.
Pre-heat your oven to 175°C ; and prepare an 8×8 inch baking pan, lining and greasing it with parchment paper.
Whisk together the flour, baking powder, sea salt and cinnamon; set aside.
Once the browned butter has cooled down, add the brown sugar to it, beating until well blended.
Next add the egg, beating again until combined. Then whisk in the vanilla extract and coffee.
Using a rubber spatula, gently fold in the dry ingredients mixture until all the ingredients are just combined with a uniform consistency. Take care not to over-mix (this will let in more air into the mixture, as well as catalysing gluten development).
Finally, fold in the chocolate chips and chopped hazelnuts.
Bake the blondies for 17 – 24 minutes. Remove them from the oven when they look *almost done*. The edges will have browned, but the centre will look a tad underdone (with a slight wobble). Be careful not to over-bake in the oven, as if you do, your blondies will be less moist, instead becoming hard.
In fact, the blondies will continue to bake and firm up as they cool (in the pan) on a wire rack. Slice into squares once the blondies have completely cooled and tuck in!