Heat the olive oil in a skillet over medium high heat on the stove.
Season the chicken thighs on both sides with salt and pepper to taste.
Saute the chicken thighs until crispy and browned on both sides, and cooked mostly through. Remove the chicken and set aside.
Drain the oil from the skillet.
Reduce the heat to medium, and melt the butter in the same skillet that you cooked through chicken in.
Add the onions to the skillet, and saute until softened.
Pour the chicken broth and heavy whipping cream into the skillet, and simmer until thickened.
Mix in the parmesan cheese, pesto sauce and tomatoes.
Add salt and pepper to taste.
Return the chicken to the skillet, and toss to coat in the sauce.
Simmer until the chicken is fully cooked through.
Serve garnished with fresh chopped basil.