Rinse and pat dry the chicken. Cut into 1-inch pieces and toss with salt and flour to coat.
In a large skillet over medium-high heat add the oil and sauté the chicken. Turn to brown on all sides. Add more oil if needed. Transfer to a platter and keep warm (See Note 1).
Add the diced onion and sauté for two minutes. Add the sliced mushrooms and continue to cook for 3-4 minutes.
Add the chicken stock and deglaze the pan by scrapping up bits of browned food on bottom of pan and bring to a boil. Add the pesto (reserving 2 tablespoons) and lower heat to simmer. Stir to incorporate and add the cream (See Note 2). Allow to reduce and thicken for several minutes. Add the chicken and platter juices back to the pan and toss to coat.
Add the cooked pasta, tomatoes and stir. Serve warm with reserved pesto on top.
1. I place the platter in the microwave to stay warm, but don't turn it on. 2. Adding the half cup of Parmesan cheese is optional, but adds a richness that's so good to the sauce.