Baked ravioli with spinach

Ingredients:

• 500 g frozen cheese ravioli
• 280 g frozen chopped spinach (thaw and squeeze out excess liquid)
• 4 tbsp (60 g) unsalted butter
• 1 small onion, chopped
• 2 crushed cloves of garlic
• 2 sprigs of fresh rosemary
• 1/4 cup flour
• 2 cups whole milk
• Salt and ground pepper
• 60 g mozzarella cheese, cut into 1.5 cm cubes
• 1/4 cup grated grana padano cheese

Preparation:

1. Preheat the oven to broil. In a large roasting pan, melt the butter over medium-high heat. Add the onion, garlic, and rosemary and cook, stirring frequently, until the onion is softened and lightly browned, about 6 minutes.
2. Sprinkle with flour and cook, stirring, until the butter and flour are combined and begin to simmer, about 2 minutes. Stir in 2 cups of water, milk, 1/2 teaspoon of salt, and a couple of grinds of pepper.
   
   Bring to a boil, then reduce heat so the combined liquids are just simmering. Stir in the ravioli and cook, stirring occasionally, until the ravioli are tender and the sauce has thickened, 5-7 minutes.
3. Remove from heat. Remove the rosemary and stir in the spinach. Sprinkle with mozzarella and Grana Padano. Place the pan in the oven and cook until the cheese is golden brown and the sauce is simmering, about 5 minutes.