1. Separate mushrooms into bite-size pieces with your fingers. (Do not chop.) Set aside.
2. Fill a large bowl partially with water, and stir in lemon juice. Remove bottom and tough outer leaves of artichokes. Separate leaves gently to reach center, snip around fuzzy thistle (choke), and remove with a spoon. Trim spines off outer leaves, if desired. Cut into quarters, and place in bowl.
3. Heat olive oil in a large saucepan over low heat. Add onion, and cook 5 minutes; add garlic, and cook 5 minutes more or until onion is tender. Drain artichokes. Add mushrooms and artichokes to pan, and increase heat to medium-high. Cook about 10 minutes or until artichokes are tender. Season with salt and pepper.
4. Place cooked pasta in a Dutch oven over medium heat. Add mushroom mixture and cream; cook until thoroughly heated and slightly thickened. Sprinkle with Parmesan, and serve.