How to Make It
Preheat oven to 350 degrees F.
Meanwhile, in a medium skillet over medium heat, cook pork, stirring and breaking it up into bite-sized pieces, until no longer pink, 5 to 6 minutes. Remove from heat, add chili powder and salt to taste, then set aside.
Arrange 1/4 of chips on a large ovenproof platter or a 2- to 3-quart baking dish, then use a slotted spoon to arrange 1/4 of the pork on top. Top with 1/4 of cheese, 1/4 of beans, and 1/4 of scallions. Repeat 3 times, making 4 layers. Bake until cheese is melted and nachos are heated through, about 30 minutes (if the top gets too brown, loosely cover with foil).
While nachos are baking, in a small bowl, combine sour cream and chipotle. Add more chipotles to taste and set aside.
Top nachos with the sour cream mixture and salsa. Serve hot, with additional salsa on the side.