The baking sheet will have the juices that the mushrooms and meatloaf have released, and you don’t want them sitting in that, so transfer to a storage container if not eating them right away.
As the pancetta crisps, it renders some of its fat which bastes the meatloaf and keeps it moist. If you don’t have pancetta, you can always cut up strips of bacon, but use thinly sliced strips.
These mushrooms are so hearty and filling that it just needs a side salad to finish the meal.
I consider this a low carb meal even though there are breadcrumbs. But for people who are really strict, they can easily swap the breadcrumbs for almond flour.