Cream the butter and sugars

• In a large mixing bowl, add the cold cubed butter and whisk until slightly creamy.
• Add the caster sugar and light brown sugar, then whisk until well combined and fluffy.

Add the wet ingredients and chocolate

• Add the egg, egg yolk, vanilla extract and chocolate chunks.
• Whisk until fully incorporated.

Fold in the dry ingredients

• Add the flour, baking powder, baking soda and salt.
• Gently mix until just combined, without overmixing.

Shape the dough

• Place the cookie dough balls onto a square baking tray, pressing them into an even layer.

Bake

• Preheat the oven to 175 °C (350 °F).
• Bake until the tops are lightly golden while the centres remain soft.
• If the top turns golden but the inside is still very raw, cover loosely with foil and continue baking.

Cool and serve

• Remove from the oven and let cool slightly.
• Serve warm with ice cream.