In a large skillet, heat 2 tablespoons of olive oil over medium-high heat. Add the spicy Italian sausage and brown for about 5-8 minutes, stirring frequently until caramelized. Lower the heat, then stir in the chopped red pepper and pumpkin puree. Pour in the vodka and milk, season with oregano, red pepper flakes, and salt, and simmer for 15 minutes until thickened.

Bring a large pot of salted water to a boil. Add the jumbo pasta shells and cook according to the package instructions until they are al dente, typically about 10-12 minutes. Once cooked, drain the shells and rinse them under cool water to prevent sticking. Set the shells aside as you prepare the filling.

In a mixing bowl, combine the ricotta cheese, shredded fontina cheese, and half a cup of basil pesto. Stir until well blended and creamy.

Spread three-quarters of the prepared sauce in a greased baking dish. Carefully stuff each pasta shell with the cheesy filling and arrange the stuffed shells in the dish. Pour the remaining sauce over the shells and finish with torn mozzarella.

Preheat your oven to 350°F (175°C). Place the assembled dish in the oven and bake for 20-25 minutes, until the cheese is melted and bubbly. Let it rest for 5 minutes before serving.