1. Cook pasta according to package directions. While pasta is cooking, wash chard and remove stems; set them aside for another use. Chop leaves coarsely. Over medium-high heat, heat a large non-stick pan. Add onion and sprinkle it lightly with salt. Cook, stirring, until onion begins to brown. Add garlic, red pepper flakes, and mushrooms and reduce heat. Cook, stirring, until mushrooms soften, adding a tablespoon or two of water if needed to prevent sticking. Add tomato paste and water and stir to combine. Add chickpeas and simmer until pasta is done.
2. When pasta is cooked, remove and reserve 1 cup of cooking liquid before draining. Add 1/2 cup of liquid to chickpea mixture. Stir in chard and cover. Cook until chard is just wilted, about 2-3 minutes. Stir in pasta, add additional pasta water if necessary to moisten, and add salt and pepper to taste. Just before serving, stir in orange juice or balsamic vinegar.