I've never been able to cook a scalloped potato dish in 60min. I keep covered until potatoes are tender then I uncover and continue to cook until they are brown on top. Usually closer to two hours. But I guess it depends on the size of batch and cooking vessel.

If it's otherwise done--if it's nicely browned on the top and bottom, I'd microwave it for two or three minutes, cover it tightly and let it rest for a few more minutes.

I agree, cover and return to the oven. You may need to add a bit more liquid as well.

I'd cover and return to the oven.