Brown the butter

• Chop the butter into cubes so it browns evenly and melt it in a saucepan.
• The butter is ready once the bubbling slows and brown milk solids appear at the bottom of the pan.
• Pour into a heatproof dish and leave to cool slightly.

Mix the sugars, yolks and milk

• Whisk the brown sugar and white sugar into the cooled butter for gooey centres and crispy edges.
• Add the egg yolks and milk and mix until fully combined.

Add the dry ingredients

• Add the flour, bicarbonate of soda, baking powder and cornstarch.
• Mix until just combined into a soft dough.

Fold in the chocolate

• Fold the chopped milk chocolate and dark chocolate into the dough to create pools of chocolate.

Chill the dough

• Scoop the dough into balls and chill in the fridge so the flour hydrates.

Bake the cookies

• Place the dough balls on a baking tray and bake at 180 °C until the edges are crispy and the centres still gooey.