Brown the butter

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

Mix the wet ingredients

• Whisk the brown sugar and granulated sugar into the warm brown butter.
• Beat in the egg, egg yolk and vanilla extract until smooth and glossy.

Add the dry ingredients

• Whisk the flour, baking soda and salt together.
• Fold the dry mix into the wet ingredients just until combined, then stir in the chopped chocolate.

Chill the dough

• Cover the dough and refrigerate until firm.

Bake the cookies

• Preheat the oven to 180 °C and line a baking tray.
• Scoop balls of dough onto the tray, spacing them apart.
• Bake until the edges are set and the centres still soft.

Cool and serve

• Let the cookies rest on the tray, then transfer to a cooling rack.
• Serve warm cookies over scoops of vanilla ice cream.