Give the potatoes a scrub but leave the skins on. If any are particularly large, halve them so that they all cook at the same speed. Pop them into a pan of cold salted water, along with a bay leaf, and bring them to a boil. Cook for 10-12 minute until just cooked. Drain them immediately and leave to cool slightly.
While the potatoes are cooking, throw the onions and bacon into a frying pan with 1 tbsp of oil. Cook them over a gentle heat for 15-20 minutes until the onions have softened completely and they have both started to brown. Add the thyme leaves and tip in the wine. Let it bubble away until the wine has reduced by half. Remove from the heat.
Cut the potatoes into thick slices. Put a fresh frying pan on the heat and add a dash of oil. Fry the potatoes until lightly coloured on both sides. Depending on the size of your pan, you may want to do this in batches.
Split the garlic clove and vigorously rub a 20cm diameter oven dish with the cut sides. Mix the potatoes together with the bacon and onion mix and transfer half of it to the oven dish. Cut the Tunworth in half horizontally and sit one half on top. Now, pile on the remaining potato and onion mix before finishing with the second half of cheese, rind side up. Transfer to the oven a bake for 20-25 minutes until melted, golden and gooey.
Meanwhile, prepare and mix your salad ingredients. Dress with lemon juice and olive oil to taste as the tartiflette is pulled from the oven. Serve immediately.