Mix using a stand or hand-held mixer and add the egg. Mix until fully incorporated.
Butter the skillets and fill half of the batter in each. Reserve.
Mix the butter with the brown sugar. Then add all the other ingredients finishing with the flour and chocolate chunks.
We're not using half of the dough so you can freeze for future baking or use it to make cookies.
Divide the dough that we're using in two and flatten out on your hands so that it's a bit smaller than the skillet. Place the dough on top of the brownie dough and press down slightly so it sinks to the same level as the brownie.
Top with extra chocolate chunks and cover the skillets in tin foil making sure that it doesn't touch the surface of the cookie.
Take to a preheated oven at 180C for 25min. Serve hot with vanilla ice cream.