I have always loved mashed potatoes, but have never liked the dry kind unless smothered with real butter. I make two kinds of mashed/whipped potatoes - and they can be mixed and varied. I love them whipped and smooth, but NOT runny. It always depends on the ingredients and how big the potatoes really are.
2 pounds of Idaho Russet potatoes (5-6 potatoes)
1/2 can evaporated milk (get a named brand)
1/4 cup butter (I usually add 1/2 cup mayonnaise or sour cream)
1 tsp sea salt
1 heaping tsp of baking powder
Skin, pare, & cut potatoes into chunks. Then bring salted water to a boil, add potatoes. Bring it to a boil again. Turn down the heat so it won't spill, and then I add some butter or a little olive oil so it won't bubble out, and cook until tender. That takes about 30-35 minutes.
Drain potatoes, put back on heat to warm up and steam off some of the left over water. Be sure you watch it so it doesn't burn.
Mash, then whip so there are no lumps....THEN add the butter, then the mayonnaise or sour cream, and salt to taste. Add the evaporated milk very slowly while whipping on slow (you don't want to splatter) until it is to the consistency you like - don't make soupy if you like your potatoes to stand up on the plate. Otherwise they will be like gravy. Ugh.
Now whip in the baking powder and then let it set on the stove for about 10 minutes - if you can, keep it on a very low heat as long as it doesn't burn. Otherwise, warm a bit, cover, turn it off and then leave on the burner you were using (I usually do this because I've burned it tooooooo many times!).