Preheat oven to 350°F (175°C). Cook pasta shells until al dente, then drain and cool.
Brown sausage in an oven-safe pan over medium heat for 4-5 minutes, then remove and setaside. Add butter and garlic to the pan, season, and cook for 1-2 minutes. Stir in Italian seasoning, wine, 1 cup pumpkin purée, and milk. Return sausage and simmer for 15-20 minutes.
Mix the remaining pumpkin purée, ricotta, egg, ¼ cup pesto, red pepper flakes, nutmeg, half the cheese, and greens for the filling.
Fill shells with the pumpkin mixture, add greens to the sauce, nestle shells in, top with cheese, and bake for 20-25 minutes.
Garnish with pesto and herbs, serve and enjoy!