Preheat the oven to 220 C, 200 fan, Gas 7. Fill a large pan of water to cook the pasta and add the potato cubes. Put it on to boil and when it boils let it bubble away for 5 minutes.
After 5 minutes add the pasta and cook until almost al dente- about 2 minutes less than specified on the packet.
Meanwhile heat the garlic oil in an ovenproof pan that can later take the cooked pasta and other ingredients. Add the pancetta cubes and cook for 45 minutes, stirring often until the fat begins to render, then add the chopped shallots and thyme.
Cook the pancetta and shallots together, stirring occasionally, for 4-5 minutes or until the pancetta is crisping up and the shallots are soft. Remove the pan from the heat and set aside until the pasta is nearly ready.
A couple of minutes before the pasta is ready return the pan to the heat. When it starts to sizzle again add the wine or vermouth and let it bubble away. Add the cream and a good grating of nutmeg and stir well. Take off the heat.
Check that the potatoes are tender and the pasta slightly al dente then remove from the heat and reserve a good cupful of the cooking liquid. Drain the pasta and potatoes and return to the pan.
Pour the creamy pancetta shallot mixture over the pasta and toss together well, adding about half a cup of the cooking liquid as you go. You may need more- the sauce should be quite runny at this point as the pasta will soak it up.
Add half the cheese and toss again. When it is well incorporated add most of the remaining cheese, leaving just enough to scatter over the top before it goes into the oven.
Toss again and tip everything into the ovenproof dish. The dish can be prepared up to this point in advance and once cooled be covered and refrigerated for up to 2 days if you like but bring it back to room temperature before cooking.
Sprinkle with the remaining cheese and put into the preheated oven or until the top is a pale gold. ( If the pasta is cold when it goes in the oven it will need about 30 minutes and to check that it is piping hot all the way through.)
Once cooked let it stand out of the oven for 10 minutes before serving.