Season the chicken breast(s) on both sides and chop into 1" pieces.

Heat 1 tablespoon of the oil in a large sauté pan over medium heat. Add the chicken and cook, stirring occasionally and lightly browned and cooked through, about 5-6 minutes. Transfer chicken to a bowl and set aside.

Add the remaining 1 tablespoon of oil to the now empty pan and add the mushrooms. Season with salt and pepper to taste, and sauté until the liquid has evaporated and the mushrooms have softened, about 5 minutes. Add the garlic and cook 30 seconds longer.

Add the pasta and water and stir well. Bring to a boil, then reduce the heat to medium low and simmer for 10-12 minutes or until the pasta is tender and has absorbed most of the water. The pasta will release it's starches when it's close to being done…it will begin to stick together and the liquid will thicken.

Add the chicken back to the pan along with the pesto sauce and tomatoes and stir well, cooking until just heated through.

Remove from heat and top with the grated parmesan. Serve topped with toasted walnuts if desired and enjoy!