Put the bacon fat into the skillet and heat until hot. Add the potatoes and onions and cook without turning for 5-8 minutes. When they look like they are starting to brown on the bottom, add the jalapeño and about 1/3-1/2 cup water to the pan. Cover the skillet and cook for about 12-14 minutes or until the potatoes are tender when pierced with a knife. When tender, remove lid and continue to fry until potatoes are browned on all sides.