1. Heat the oven to 300°F. Stack the tortillas and roll them up in a sheet of foil. Put them in the oven to warm while you cook the filling.
2. Put the pumpkin seeds in a large skillet over medium heat. When they have puffed and browned a bit, add the oil, kale, beans, and scallions. Sprinkle with the chili powder and salt and pepper.
3. Mash the black beans with a fork or potato masher and add a spoonful of the reserved liquid if the mixture seems dry. Cook for 10 minutes, stirring occasionally. Turn off the heat and season with the lime juice. Taste and adjust the seasoning.
4. To roll each burrito, lay a tortilla on a flat surface and put 1⁄4 of the filling (or 1/8 if you’re using small tortillas) on the tortilla. Season with some hot sauce, if desired.
5. Fold the tortilla over from the bottom to cover the beans and greens, then fold in the 2 sides to fully enclose them; finish rolling and put the burrito seam side down on a plate.
6. You can wrap them individually and refrigerate or freeze them at this point. Reheat in the microwave as needed.