Spinach Gratin Recipe

Bahan-bahan (13 porsi)

• 3 tbsp whipped butter (I used Land O Lakes)
• 1 cup finely chopped onion
• 1/4 cup all purpose flour (or gluten-free flour mix)
• 1/4 tsp fresh grated nutmeg
• 3 cups 2% milk
• 3 lbs frozen chopped spinach (defrosted, I used 3 16-oz packages )
• 3/4 cup Parmesan cheese (freshly grated )
• 1 tbsp kosher salt
• 1/2 tsp black pepper (freshly ground )
• 1/2 cup Gruyere cheese (shredded or Swiss cheese)