Preheat oven to 350 Degrees F and prepare an 8x8" glass baking dish with a quick spray of cooking oil.
Heat 1 tablespoon vegan margarine in a pan. Add onion, celery and mushrooms and saute for a few minutes. When mushrooms give off liquid, add soy sauce. Keep cooking until all vegetables are tender, turn off heat.
In a medium soup pot, melt the remaining 3 tablespoon vegan margarine over low heat. Stir in the flour and whisk for a few minutes. It will get thick. Start adding the broth bit by bit, whisking all the while and bring to a boil. Add the soymilk little by little and continue to stir and simmer. Add the mushroom/celery/onion mixture and lemon juice. Season with salt, pepper and some paprika. Add the mashed chickpeas a spoonful at a time to break it up evenly throughout the sauce.
Cook pasta until al dente, approximately 9 minutes. Drain and return it to the pot. Add the mushroom sauce to the pasta and stir gently to combine. Transfer the mixture to the baking dish. Cover tightly with foil and bake for 15 minutes. Uncover the dish and sprinkle crushed chips and french fried onions on top and bake for another 5-6 minutes or so or until the top is browned and crispy.