01 -
Grease your 8x8 casserole dish thoroughly with butter.
02 -
Evenly lay the potatoes across the bottom of the dish.
03 -
In a small saucepan, combine milk, cream, mustard, salt, nutmeg, and pepper.
04 -
Heat the mixture over medium heat, stirring often, until it's just about to boil (5-10 minutes).
05 -
Reduce the heat, add the cheese to the pan, and stir until it's melted and smooth.
06 -
Carefully pour the cheese sauce over the layer of potatoes.
07 -
Leave it to cool off a bit before the next step.
08 -
Place the pre-cut butter slices across the top of the potatoes.
09 -
Sprinkle a little paprika over everything.
10 -
Wrap the dish tightly with plastic wrap.
11 -
Pop it in the fridge for at least 12 hours, or overnight if you can.
12 -
Warm up your oven to 350°F.
13 -
Bake uncovered for 45 minutes until golden and bubbly.