Instructions

1. Preheat the oven to 350°F and generously grease a 10 inch cast iron skillet with butter. Set aside.
2. In a large mixing bowl combine the melted butter, and brown sugar. Beat until mixed together. Add in the eggs, egg yolk, and vanilla extract. Mix well.
3. In separate bowl mix together the flour, salt, and baking soda. Add the dry ingredients into the wet and mix until combined. Add the oats, chocolate chunks, and toffee pieces and use a rubber spatula to fold together to evenly distribute.
4. Transfer the cookie dough to your prepared skillet and pat into an even layer.
5. Bake at 350°F for 35 to 40 minutes, or until the edges are just golden brown and the center has puffed up but is still very gooey in the middle.
6. Allow to cool for at least fifteen minutes before serving with vanilla ice cream. Best served warm!