Spinach and Mushroom Stuffed Shells

Name: Spinach and Mushroom Stuffed Shells
Ingredients: 1 1/2 tsp. kosher salt, plus more for the pasta; 12 oz. jumbo pasta shells (25 to 30); 2 tbsp. olive oil; 1 lb. cremini mushrooms, thinly sliced; 2 tsp. fresh thyme, chopped; 4 garlic cloves, minced; 2 16-ounce containers whole-milk ricotta; 3 scallions, chopped; 1 large egg, beaten; 2 c. shredded low-moisture mozzarella; 3/4 c. grated parmesan; Black pepper, to taste; 2 tbsp. salted butter; 2 tbsp. all-purpose flour; 1/2 c. dry white wine; 3 c. half-and-half; 1 5-ounce package baby spinach, chopped; 2 tsp. grated lemon zest; Green salad, for serving