Thinly slice the potatoes (no need to peel). Peel and finely chop the garlic.
In a large ovenproof dish, layer 1/4 of the potatoes over the bottom and top with 1/3 of the garlic cloves. Repeat until all of the potato and garlic has been used.
Pour over the vegetable stock, then the cream. Add a pinch of salt and pepper, then sprinkle the pancetta and thyme leaves over the top.
Put in the oven for 40 minutes until the potatoes are soft and the pancetta is golden and crisp. If the pancetta looks like it is cooking too quickly, cover with foil.