Reduce heat to medium and allow sauce to simmer for 15 minutes or until sauce is reduced by 2/3, stirring occasionally.
When sauce is done, cover with a lid and set aside while you cook the chicken.
For Chicken:
On a large saute pan or skillet, heat olive oil over medium-high heat.
Season both sides of pounded chicken breasts with salt, pepper and Italian seasoning blend.
Sear chicken until golden on the first side without shifting it around on the skillet, (about 4 minutes).
Flip chicken over and sear on the other side for about 4 minutes. Continue cooking until chicken feels fairly solid (not squishy) in the center when you press it with your finger.
Remove chicken from heat and place on a platter. Cover with tin foil and allow chicken to sit (uncut) for 5 minutes.
Top chicken brests with marsala sauce and mushrooms. Serve hot! Enjoy!