Heat a large skillet over medium-high heat.
Mix the salt and pepper and sprinkle on chicken.
Add the olive oil and when oil shimmers, place chicken in the pan.
Brown the chicken well on one side; remove to a plate.
In the same pan, add the mushrooms and sear over high heat, stirring often.
Add the chicken stock, balsamic vinegar, bay leaf, thyme and garlic to the pan; stir to combine.
Place the chicken, unbrowned side down, in the pan. Bring to a boil, reduce heat to low, cover and simmer for 10 minutes.
Remove cooked chicken to a plate and keep it warm. Remove the garlic and bay leaf; discard both.
Place butter in the pan and stir until melted.
Turn the heat up to medium-high and reduce the sauce 50%. This should take about 5-7 minutes.
Return the chicken to the pan to heat through.
Serve over pasta.