Butternut Squash Lasagna

Name: Butternut Squash Lasagna
Ingredients: 1 butternut squash (roughly 3 cups once diced); 4 tbsp olive oil; 2 cloves garlic (chopped); 1.5 pounds fresh spinach; 1 lemon (zested and juiced); 14 ounces lasagna sheets; 14 ounces fresh mozzarella (torn into pieces); 4 ounces parmesan cheese (grated ); Kosher salt and freshly ground black pepper; 2 tbsp unsalted butter; 1/4 cup flour; 2.5 cups whole milk; 1 bay leaf; grated nutmeg to taste; 4 ounces parmesan cheese (grated); Kosher salt and freshly cracked black pepper