with cooking oil spray. transfer the meat mixture into the casserole and spread the mashed potatoes over the top, leaving a small border around the edge.
bake until potatoes brown and the juices bubble around the edge, about 40 minutes. let cool for 10 minutes before serving.
put potatoes and salt in a pot with enough water to cover the tops by a couple of inches. bring to a boil, then reduce heat and simmer until fork tender, ~12-15 minutes. drain and return the potatoes to the pot.
on low to medium heat, mash the potatoes until all of the excess water is absorbed and they start to look dry and dusty. slowly 