01 - Set oven to 375°F (190°C) and allow to fully preheat.
02 - Carefully slice the top off the pumpkin to create a lid. Scoop out seeds and stringy pulp. Lightly season the interior with a pinch of salt and pepper. Set the pumpkin on a parchment-lined baking sheet.
03 - Place the prepared pumpkin (lid set aside) in the oven. Bake for 25 minutes until the flesh is slightly soft but the pumpkin remains structurally intact.
04 - Bring a large pot of salted water to a boil. Add the macaroni and cook until just al dente, about 1–2 minutes before the package timing. Drain and set aside.
05 - Melt 2 tablespoons butter in a medium saucepan over medium heat. Add the flour and whisk for 1 minute. Gradually pour in the milk and cream, whisking continuously. Cook until the mixture thickens and begins to bubble, about 3–4 minutes.
06 - Lower the heat. Stir in grated cheddar, Gruyère, and Parmesan until smooth. Add salt, pepper, nutmeg, and Dijon mustard. Remove from the heat once cheeses are fully melted.
07 - Fold the cooked macaroni into the hot cheese sauce. Mix until noodles are evenly coated.
08 - Spoon the macaroni and cheese mixture into the partially baked pumpkin, allowing space for bubbling. Do not overfill.
09 - In a small bowl, combine panko breadcrumbs, melted butter, grated Parmesan, and parsley. Sprinkle evenly over the filled pumpkin.
10 - Return the pumpkin (without its lid) to the oven and bake for 40–45 minutes, until the filling is bubbling and the pumpkin flesh is exceptionally tender when pierced. If desired, bake the pumpkin lid alongside for the final 15 minutes.
11 - Allow the pumpkin to rest for 10 minutes before serving. Scoop portions that include both cheesy pasta and some roasted pumpkin flesh for optimal presentation and taste.