Transfer a single or two serving of scalloped potatoes into a microwavable container.

You can drizzle it with 2 T of milk or water to add some moisture. Cover with a lid.

Microwave your scalloped potatoes on high (or if you have a reheat setting, even better) for one minute. Remove and use a rubber spatula to gently flip some of the potatoes. Stirring too hard will cause the delicate potato slices to mash. 

Heat for 25-second increments until thoroughly heated.

You want to keep this creamy, so add a bit more water or milk as you go, but not too much at the start.