Such an easy recipe that's a proven crowd pleaser! Serve in the skillet topped with ice cream and liberally drizzled with chocolate sauce – just hand everyone a spoon. Or cut into slices and serve – easiest dinner party dessert ever.
Preheat the oven to 180C | 350 F. Wipe a 20cm / 8in iron skillet (a slightly larger one will also work but you might need cook for less time) with a little oil.
Beat the butter and sugar in a stand mixer fitted with a paddle attachment (or use a hand mixer).
Add the egg and beat to combine, scraping the sides of the bowl as needed.
Add the flour, salt, baking powder, bicarbonate of soda, cinnamon and nutmeg if using. Beat to combine or mix everything together with a spoon.
Add the rolled oats and beat them in (or fold in with a spoon).
Use a wooden spoon to fold in the chocolate buttons. You might want to reserve a few to arrange over the top of the cookie. That does nothing to the taste, it just looks good!
Press the cookie dough into the skillet and smooth. Bake for 30-35 minutes – do check at the 25 minute mark if you are using a larger skillet – the edges should be cooked but the middle can be a little soft and squidgy. Cool slightly before serving - the cookie will get firmer as it cools down.
While the cookie is cooling, put all the ingredients for the chocolate sauce into a small pot and heat gently, stirring until the chocolate has melted and sauce is smooth. If it is too thick you can add a splash of milk to thin it out.
Either serve the cookie in the skillet topped with vanilla ice cream and drizzled with chocolate sauce and allow everyone to dig in or cut into slices before serving.