1. Heat a large nonstick skillet over medium-high heat. Add olive oil to pan; swirl to coat. Add mushrooms, sliced onion, salt, and pepper to pan; sauté 5 minutes. Stir in garlic, and sauté 30 seconds. Add vinegar; cook 30 seconds or until liquid almost evaporates.
2. Arrange half of mushroom mixture over half of each tortilla. Top each tortilla with 1/2 cup chicken, 1/2 cup arugula, and 1/4 cup cheese; fold tortillas in half.
3. Wipe pan clean with a paper towel. Heat pan over medium heat. Coat pan with cooking spray. Add tortillas to pan. Place a heavy skillet on top of tortillas; cook 2 minutes on each side or until crisp.
Watermelon-jicama salad: Combine 4 cups (1/2-inch) cubed seedless watermelon, 1 1/2 cups (1/2-inch) cubed peeled jicama, 1 cup chopped English cucumber, and 1/2 cup chopped red onion. Add 2 tablespoons fresh lemon juice, 2 teaspoons sugar, and 1 teaspoon olive oil; toss well.