Pre-heat the oven to 160°C / 140°C fan assisted /gas mark 3 / 320°F.
Peel the potatoes and cut the smaller potatoes in half and the larger potatoes in quarters, then place into a large casserole dish.
Pour in the cream and milk and ensure the potatoes are fully submerged and then add the butter, bay leaves, cloves, black peppercorns, salt, garlic cloves and thyme.
Put the lid on the casserole dish and bake in the oven for 1½ hours until the potatoes are cooked all the way through.
Remove the dish from the oven then turn the heat up to 200°C / 180°C fan assisted / gas mark 6 / 400°F. Pour the olive oil into a roasting tray and place in the oven for 10 minutes for the oil to heat.
Drain the potatoes into a colander set over a large pan to catch the cream*. Shake the colander a little to bash the potatoes around a little then place a tea towel over the colander so the potatoes steam for 10 minutes.
When the oil is hot, remove the roasting tray from the oven and tip the potatoes onto the tray, turning in the oil to cover.
Place in the oven to roast for 45 minutes, turning the potatoes every 15 minutes.
Remove from the oven and serve immediately.