Brown the butter

• Melt the butter in a saucepan over medium heat.
• Keep cooking until it turns golden brown and nutty, then let it cool slightly.

Mix the sugars and eggs

• Whisk the brown sugar and white sugar into the browned butter.
• Add the egg, egg yolk and vanilla extract and whisk until smooth.

Make the dough

• Add the flour and baking powder and mix until just combined.
• Fold in the chocolate chips.

Chill the dough

• Shape the dough into balls and place them in the fridge.

Shape and top

• Form the chilled dough into balls again and place them on the baking sheet, spaced apart.
• Scatter chocolate chips and sea salt on top.

Bake

• Bake in a preheated oven at 180 °C until the edges are set and golden and the centers are thin and crisp.
• Let the cookies cool on the tray before serving.