Pat dry the chicken and season with salt and pepper.
On a grill or in a grill plan, cook the chicken on each side for 5-6 minutes.
Add a piece of beefsteak tomato on top of each of the pieces of grilled chicken.
Top the tomato with a little pesto.
On top of the pesto, add a slice of mozzarella cheese, then bake until the cheese melts, or if you're still using the grill, turn the heat down to medium and cook until the cheese melts.
Add a drizzle of balsamic and serve.
Notes
Use thinly sliced chicken breast rather than a thicker cut. You can opt to buy thin cut already or filet them yourself.
Season the chicken! You can use an Italian seasoning blend, or just a simple salt and pepper (I love using salt and pepper and keeping it super simple when I grill chicken)