Red and Green Stuffed Shells

Name: Red and Green Stuffed Shells
Ingredients: 1 tbsp. Olive Oil; 1/2 whole Onion, Diced; 1 clove Garlic, Minced; 10 oz. weight Fresh Baby Spinach; 4 tbsp. Butter; 1/4 c. All-purpose Flour; 2 1/2 c. Whol Milk, More If Needed; 2 tbsp. Chopped Basil; 2 tbsp. Chopped Parsley; Salt And Pepper, to taste; 30 oz. weight Whole Milk Ricotta Cheese; 1 c. Grated Parmesan Cheese, Plus More For Sprinkling; 1 whole Large Egg; 12 oz. weight Jumbo Pasta Shells (25 To 30 Shells) Cooked Until Slightly Firmer Than Al Dente