Ingredient:

• 1/3 cup butter, cubed
• 1 medium onion, chopped
• 1 garlic clove, minced
• 1/2 cup all-purpose flour
• 1 teaspoon salt
• 3-1/2 cups 2% milk
• 4 cups shredded part-skim mozzarella cheese, divided
• 1 cup grated Parmesan cheese, divided
• 1 teaspoon dried basil
• 1 teaspoon dried oregano
• 1/2 teaspoon white pepper
• 1 carton (15 ounces) whole-milk ricotta cheese
• 1 tablespoon minced fresh parsley
• 9 lasagna noodles, cooked and drained
• 1 jar (8.1 ounces) prepared pesto
• 2 packages (10 ounces each) frozen chopped spinach, thawed and squeezed dry