Use immersion circulator to heat water to 145 degrees.
In a small bowl, stir together pesto, sour cream, sun-dried tomatoes, lemon juice, salt, pepper, basil, thyme, onion, and garlic. Add chicken and stir so that chicken is well coated.
Divide chicken and sauce evenly among 4 bags which are safe for sous vide cooking (I prefer to vacuum seal bags).
Cook at 145 degrees for 2 hours.
Remove bags from water and then remove chicken from bags. Pour liquid from bags into a bowl and set bowl aside (you will use this for the sauce).
Heat olive oil in a large skillet over medium high heat. Add chicken to skillet and cook until browned on each side, about 2-3 minutes per side.
Remove chicken from skillet. Reduce heat to medium-low.
Pour reserved liquid into pan. Whisk cornstarch into pan. Continue whisking until mixture has thickened, about 1-2 minutes.
Return chicken to pan and coat with sauce. Serve chicken with sauce.