Pierce potatoes in several places with fork. Bake in 400 degree oven until potatoes feel soft when squeezed (about 1 hour). Let potatoes stand until cool enough to handle. Cut each potato lengthwise into quarters. With a spoon, scoop flesh from skins, leaving 1/8" thick shell. Reserve flesh for other uses. Brush potato inside and out with butter. Place, skin side down, in a single layer on a 12" x 15" baking sheet. Bake in a 500 degree oven until crisp (about 2 minutes). Remove from oven and distribute cheese among skins, filling equally. Broil 4" below heat until cheese is melted (about 2 minutes). Serve with chile salsa for dipping.