spinach Gratin- Barefoot contessa

5 boxes of frozen spinach thawed

2 Large yellow onions chopped

1/2 stick butter

1/4 cup flour

1/4 tsp nutmeg

1 cup cream

2 cups milk

1 cup grated parmesan

1 Tbl kosher salt

1/2 tsp pepper

1/2 cup gruyere

Preheat to 425

In large saucepan melt butter, add chopped onions and let cook over med heat for 15 minutes

Add flour and nutmeg. Cook 2 more minutes

Add cream & milk, cook until thick

Add spinach (thawed and squeezed of all liquid) & 1/2 cup grated parmesan, salt and pepper

Cook for 5 minutes

Transfer to baking dish. Cover with gruyere and remaining parmesan

Cook for 20 minutes, or until bubbly