On a casserole pan boil the potatoes with 1 tablespoon of salt. Boil until potatoes are 75% cook, about 10 minutes. Drain and set aside to cool. Peel potatoes and cut in to ½ inch slices.
Meanwhile char the poblanos over direct flame on gas stove top. Allow the skin to blacken and bubble up, flip the poblanos to blacken every side. Put the roasted/charred poblanos in plastic bag to sweat. Set aside until cool and remove poblano skin, seed, and vein. Cut into strips.
Preheat oven to 350 F. Grease with butter a casserole baking dish, arrange a layer of potatoes on the casserole, top with a layer of cheese, top with poblanos and sprinkle with salt. Repeat as many layers as the casserole fit.
In a mixing bowl mix the Mexican crema and the jalapeno salsa. Pour on the casserole as much crema mix it fits. Cover loosely with aluminum foil. Put casserole on a baking sheet to catch any drips of sauce or cheese.
Put in the oven and let cook for 30-40 minutes until crema start boiling. Remove the foil cover after 20 minutes in oven.
Remove from the oven and let cool down before serve.