Green Bean Casserole

For the onions:

2 tbsp butter

2 or 3 yellow onions, sliced

salt and pepper to taste

1 tbsp sherry vinegar (stirred into the onions after they are caramelized)

For the white sauce:

2 tbsp butter

2 1/2 tbsp flour

2 1/2 cups milk

pinch of nutmeg

cayenne to taste

1/4 tsp dried thyme

salt and pepper to taste

For the topping:

2/3 cup panko or other style bread crumbs

2 tbsp melted butter

For the rest:

2 lbs green beans, trimmed, blanched

salt and pepper to taste

4 oz grated Gruyere cheese, divided

1/3 cup grated Parmesan cheese

Bake 30-45 minutes at 375°

We made this for the holidays with one bag of Costco's fresh green beans and it was delicious!