Preheat the Oven
Preheat your oven to 350°F (175°C). Lightly grease a 10–12 inch oven-safe skillet (preferably cast iron).

Brown the Butter (Optional but Recommended)
In a saucepan, melt the butter over medium heat. Continue cooking, stirring often, until it turns golden brown and smells nutty (about 5–7 minutes). Remove from heat and let cool slightly.

Mix the Sugars and Butter
In a large bowl, whisk the browned butter (or just melted butter) with both sugars until combined and slightly cooled.

Add Eggs and Vanilla
Add the eggs, egg yolk, and vanilla. Whisk until smooth and slightly thickened.

Combine Dry Ingredients
In another bowl, whisk together the flour, baking soda, and salt. Gradually stir the dry mixture into the wet ingredients until a soft dough forms.

Fold in Chocolate
Fold in chocolate chips and chopped chocolate chunks until evenly distributed.

Spread in Skillet
Press the dough into your prepared skillet, spreading it evenly to the edges.

Bake
Bake for 20–25 minutes or until the edges are golden brown and the center is just set but still soft.

Cool Slightly and Serve
Let the cookie cool for 5–10 minutes before topping with vanilla ice cream. Serve directly from the skillet with spoons.