Wash the sweet pumpkin thoroughly, cut it in half, and remove the seeds.
Wrap the pumpkin in plastic wrap and microwave for 7-8 minutes.
Scoop out the cooked pumpkin flesh with a spoon.
Finely chop the onion and ham.
Melt butter in a pan and stir-fry the onion and ham.
Add the scooped pumpkin flesh, heavy cream, salt, and pepper, mix well and briefly stir-fry again.
Fill the pumpkin shells with the stir-fried filling.
Generously top with mozzarella cheese.
Bake in a preheated oven at 180°C for 10-15 minutes.