Slice the potatoes to about 2 mm thick.
Season with salt, pepper, and melted butter.
Place half of the mozzarella on a baking sheet lined with parchment paper and cover with the potato slices.
Bake in a preheated oven at 350°F (180°C) for 10 minutes.
Brown the ground meat in a pan.
Add leek, carrot, and celery. Season with salt and pepper.
Stir in the tomato paste and simmer for about 30 minutes.
Remove the potato base from the oven.
Evenly spread the ground meat filling over the potatoes.
Gently roll up, using the parchment paper as a guide if needed.
Sprinkle the rest of the mozzarella over the roll.
Return to the oven and broil for another 10 minutes at 350°F (180°C) until the mozzarella is golden brown.
