Creamy Chicken Lasagna with White Sauce

Ingredients

• 9 lasagna noodles (cooked al dente)
• 4 cups shredded cooked chicken (or rotisserie)
• 1 Tbsp olive oil
• 1 medium onion (finely diced)
• 4 Tbsp unsalted butter
• 1/3 cup all-purpose flour
• 2 1/2 cups chicken broth
• 1 1/2 cups half and half (or a mix of heavy cream and milk)
• 5 oz fresh spinach (roughly chopped)
• 2 tsp sea salt
• 1/2 tsp black pepper
• 3 garlic cloves (minced)
• 15 oz ricotta cheese
• 1 large egg
• 1/4 cup chopped parsley
• 1/4 cup grated parmesan cheese
• 3 cups mozzarella cheese (divided, reserve 1 cup for topping)