Combine the flour, salt, and pepper in a shallow bowl.
Dredge the chicken breasts in the mixture and shake off any excess.
In a large skillet, heat olive oil and 2 tablespoons of butter over medium-high heat.
Add chicken breasts and cook until they’re golden brown, about 3 minutes per side.
Remove them from the skillet and set aside.
Add sliced mushrooms to the same skillet.
Cook until they are lightly browned, then add the garlic and cook until fragrant.
Pour in the Marsala wine, scraping the bottom of the skillet to release any browned bits.
Let it simmer gently for a couple of minutes.
Add chicken stock and the remaining butter to the skillet.
Return the chicken to the pan.
Simmer for about 10 minutes until the sauce thickens and the chicken is cooked through