In a large skillet, melt 2 tablespoons of butter over medium heat. Add the onions and stir gently. Cook for 20–25 minutes, until caramelized to a deep golden brown.

Preheat your oven to 375°F (190°C). Peel and slice the potatoes evenly to ¼-inch thickness and pat them dry.

In a large bowl, combine sour cream, onion soup mix, and beef broth. Mix until smooth and creamy. Fold in the caramelized onions and half the cheese.

Grease a 9x13-inch baking dish and layer half of the sliced potatoes, followed by half of the onion mixture. Repeat layers and top with remaining cheese.

Cover with foil and bake for 30 minutes. Remove foil and bake for another 15-20 minutes until golden brown and cheese is bubbling.

Remove from the oven, let cool a few minutes, and garnish with herbs or crispy onions before serving.