Preheat the oven to 160C / 140C fan. Get a large pumpkin, cut out the lid and empty the seeds and stringy bits. Put the lid back on and place it on a large baking tray that can double as a serving dish. Bake for 30 minutes.
In a large mixing bowl, mix together the cheeses, cornflour, garlic, shallot and thyme. Put it into the pumpkin, spoon over the creme fraiche and pour in the white wine. Turn the oven up to 180C/160C fan and return the pumpkin to the oven, without the lid, for 30 minutes. Take it out of the oven and give it a good stir, then continue cooking until the fondue is completely melted together and smooth, about another 15-30 minutes.
Keep the pumpkin on the baking tray and serve immediately, with crusty baguette for dipping into the fondue, and gherkin and cured meats on the side. Use a spoon to scoop out chunks of pumpkin flesh to eat with baguette too.