Use chicken shears to cut any unwanted pieces of chicken breast. Cut chicken breast in half lengthwise. Cut chicken breast in half again going through the chicken to make a thinner breast.
Add chicken to a mixing bowl. Add mustard, 1 tsp olive oil and white wine vinegar. Stir to coat and set aside.
Heat a large skillet over medium heat. Add 2 tsp olive oil and the mushrooms and cook. Stirring occasionally until browned. Place in a large covered dish to the side to keep warm. (Note: if mushroom slices are still large, chop further)
Add three chicken breasts to the hot pan and cook approximately 5 minutes per side or until cooked through. Remove chicken to covered dish with mushrooms. Immediately place slice of cheese over each.
Add next batch of chicken breast to the skillet and repeat. Which chicken is cooking. heat a small skillet to medium high heat. Add ham slices in batches and heat about 2 minutes per side. Place on top of chicken breasts.
When all chicken is cooked through each should be topped with swiss and ham. Serve with mushroom and tomato slices.
Notes
This recipe makes 4 servings. Each chicken breast will be approximately than 2.5 ounces, plus toppings.