What follows is my adaptation; the original recipe is here.
1) Cook half a pound of elbow pasta until it's al dente. Rinse with cool water to prevent overcooking. Drain thoroughly.
2) Chop 3 smallish heads and stems of broccoli (or an equivalent quantity of green beans, or bell pepper, or whatever else you think belongs in a casserole). Leave the vegetables raw; they'll cook while the casserole is baking.
3) Heat oven to 350F.
4) Roughly chop 1 large carrot, half a yellow or white onion, 2 shallots, and 5 small Yukon gold potatoes (about 2 cups of potato); place in pot with .5 cup raw cashews, cover with 3 cups water, bring to boil, simmer covered 15 minutes. Drain, reserving the water.
5) In food processor, whir cooked vegetables, cashews, .5 cup margarine, 1 tsp salt (omit if using salted margarine), .5 tsp minced garlic, .5 tsp Dijon mustard, juice from 1 lemon, and seasonings (the recipe suggests cayenne and paprika; I used black pepper, sage, and nutmeg) with as much of the vegetable-boiling water as needed to make a very smooth, fairly liquid sauce.
5.5) Do not eat all the sauce with a spoon, no matter how tempted you are.
6) Put pasta, raw veg, and sauce in 9" x 12" pan. Mix well.
6.5) Optional: wash and dry the processor, turn four slices of stale bread and a couple of Tbsp of Earth Balance into breadcrumbs, and sprinkle the breadcrumbs over the top of the pasta. Or use pre-made bread crumbs, or don't bother.
7) Cover with foil and bake 15 minutes. Remove foil and bake 5 to 15 minutes more until sauce is bubbling, veg is no longer raw, and the breadcrumbs (if you used them) are browned.
Makes six moderate or four hearty servings.
If you use non-soy margarine, it's soy-free. According to the comments on the original recipe, those with nut allergies can skip the cashews in step 4 and add tahini in step 5 instead, though I'm not sure how much tahini. I'm sure it could be made with rice pasta or whole wheat pasta. Experiment! It's a very flexible recipe.