Preheat oven to 300 degrees F. For cheese rounds, line a large baking sheet with parchment paper or foil. Draw four 4-inch circles on the paper or foil, spacing circles at least 1 inch apart. In a small bowl combine cheese and the 1/8 teaspoon pepper. Divide mixture among circles, spreading evenly to edges.
Bake for 10 to 15 minutes or until cheese is melted and just beginning to brown on the edges. Cool on baking sheet. Carefully remove cheese rounds from paper or foil; set aside.
Meanwhile, sprinkle chicken with salt and additional pepper. In a large skillet heat oil over medium heat. Add chicken and garlic; cook about 8 minutes or until chicken is no longer pink, stirring occasionally and sprinkling with basil for the last 2 minutes of cooking.
In a large bowl toss together spinach, mushrooms, tomato wedges, and red onion. Divide spinach mixture among dinner plates. Top with chicken strips and cheese rounds. Serve with salad dressing.