Preheat the oven to 350 degrees F.
Cut the root and top end off of the garlic head, drizzle with olive oil, wrap in tin foil and roast in the pre-heated oven for about 1 hour, or until soft.
Cut a circle around the stem of the pumpkin and remove the lid. Cut the seeds off of the lid and scoop out the seeds from the inside of the pumpkin. Season the inside with salt and pepper.
In a medium-large saute pan over medium heat, brown the pancetta to release the fat. Add the leek and sweat until soft. Turn off the heat and let cool.
In a bowl, combine the croutons, cheese, thyme, nutmeg and smoked paprika. Once cooled, add the pancetta and leeks and mix to combine.
Remove the roasted garlic from the oven and squeeze the cloves out of the skins. Roughly chop and add to the mixture.
Fill the pumpkin with the stuffing mixture. Pour over the heavy cream, put the pumpkin lid back on, and place on a sheet tray covered with a rack or a silicone pad to prevent it from sticking.
Bake for 90 minutes, or until the pumpkin flesh is tender and easily pierced with a fork.
In the last 15 minutes of cooking, remove the lid from the pumpkin and top the stuffing with the extra grated gruyere. Return the pumpkin to the oven, keeping the lid on the side of the sheet tray so the cheese can brown and bubble.
Serve warm, sliced into fourths, in half, or as individual pumpkins depending on their size.