Heat a grill pan over medium/medium-high heat and spray with cooking spray. Sprinkle the chicken breast with salt and pepper and place on the grill pan and allow to cook for around 20 minutes, flipping the chicken halfway through, until a meat thermometer inserted into the thickest part of the breast reads 165 degrees.
Mix together the balsamic vinaigrette, dijon mustard, and olive oil, then brush onto the chicken breast and cook for an additional minute. Remove from grill and cut into thick slices.
In a large bowl, add the spinach, followed by the strawberries, avocado, walnuts, and Queso Fresco. Top with the sliced chicken, garnish with cilantro, and serve with dressing of choice. Enjoy!