Melt the butter in a large pan over a medium-low heat and fry the garlic for 1 min until softened. Tip in the sliced potatoes, cream and milk, and season well with salt and freshly ground black pepper. Stir continuously for 5-10 mins until the cream and milk are steaming and the liquid has thickened (it should coat the back of a spoon). Scatter in the cheese and stir until melted.

Tip into a slow cooker and push the potatoes down until submerged in the liquid. Cook on high for 4 hrs or low for 6 hrs until tender. To brown, gently transfer to an ovenproof dish and grill on high for 5-10 mins. Serve with chopped parsley scattered over. Will keep covered and chilled for two days. Cut into portions and reheat in an oven at 180C/160C fan/gas 4 for 20 mins until piping hot through. Brown under a hot grill for 5-10 mins.