Stir the Caesar salad dressing, ranch salad dressing, olive oil, canola oil, lemon juice, basil, and sugar together in a small bowl; set aside.
Rinse the stuffed olives, shake off excess water, then cut each olive in half. Combine the olives, lettuce, mushrooms, and feta cheese in a mixing bowl. Drizzle with the salad dressing, and toss to coat. Season to taste with salt and pepper. Sprinkle with Parmesan cheese to serve.
