In a large frying pan with a tight-fitting lid, cook olive oil, mushrooms, and salt, uncovered, over high heat, stirring until mushrooms start to brown slightly, 3 to 5 minutes. Lower heat to medium high, add garlic and chile flakes, and cook, stirring, until fragrant, 1 to 2 minutes. Add tomatoes, chicken broth, and chickpeas. Bring to a boil. Cover, reduce heat to low, and cook 20 minutes.
Break pasta into 2-in. pieces. Add pasta to vegetable mixture, cover, and simmer until pasta is cooked on the outside but still raw in the center, about 4 minutes. Add shrimp, cover, and cook until shrimp and pasta are cooked through, about 5 minutes. Stir in oregano and 1 tbsp. lemon juice. Sprinkle with remaining lemon juice to taste. Garnish with green onions, parmesan, and parsley. Serve hot.
Note: Nutritional analysis is per 2-cup serving.