For the black bean and chipotle pumpkin sauce:
2 15-oz cans black beans
1 15-oz can pumpkin puree
1/2 cup water
1 no-salt-added vegetable bouillon cube
1 chipotle en adobo
2 TBSP nutritional yeast
1 TBSP canola or grapeseed oil
1 generous pinch fine sea or kosher salt
1 generous pinch Mexican oregano (optional)
diced red bell pepper
chopped cilantro leaves
flaked sea salt and freshly ground black pepper
Heat oven to 375 (if assembling nachos right after making sauce—see Note).
Drain both cans of beans, but do not rinse. Add to a medium pot and set aside. Add remaining sauce ingredients to a food processor and process until very smooth, 30-60 seconds.
Add pumpkin mixture to pot with beans and bring to a boil over medium heat. Reduce heat slightly to medium-medium low. Cook, stirring frequently, until heated through and thickened a bit, about five minutes.
To assemble, pile tortilla chips snugly in a low mound in a baking dish and pour sauce over top, leaving a small border of chips uncovered (the chips touching the sauce will absorb it and soften, but the chips below and to the side will leave some crunchy chips that can scoop up toppings). Bake 15 minutes.
Remove from oven, top generously with diced pepper, cilantro, and avocado. Sprinkle top of dish gently with flaked salt and then generously crack black pepper over top. Serve at once with forks.
Note: once the sauce is done, nachos can be assembled immediately in any desired quantity or stored to assemble nachos later. Leftover sauce can be refrigerated for days and reheated as desired to make another batch.