Preheat the oven to 350º F. Have ready a nonstick 13” x 9” or 3-quart baking dish.
Boil the potatoes in enough water to cover them until they are almost tender, 5 to 7 minutes. Drain and set aside.
Put the onion and garlic in a large nonstick skillet with ¼ cup of the broth. Cook, stirring frequently, until the onion softens, about 5 minutes. Add the jalapeños and another ¼ cup of the broth and cook 1 minute. Add the chili powder, pepper to taste, the cooked potatoes, and the remaining ¼ cup broth. Mix well, then cook and stir 1 minute. Stir in the spinach, then remove the pan from the heat.
Spread ½ cup of Enchilada Sauce in the bottom of the baking dish. Lay a tortilla on a flat surface and spread about ¼ cup of potato mixture in a line down the center of the tortilla. Roll the tortilla and place it seam-side down in the baking dish. Repeat. Pour the remaining Enchilada Sauce evenly over the rolled, filled tortillas.
Cover the dish and bake for 30 minutes. Serve hot, with salsa on the side, if desired.