In a shallow bowl, combine the flour, garlic powder, salt, and pepper, stirring to combine.
Dip each chicken breast piece in the flour on each side, shaking to remove excess flour.
In a large skillet, heat 3 tablespoons of butter over medium-high heat.
Once melted, add the chicken breast pieces. Cook for 3-4 minutes on each side, until browned. The pieces do not need to be cooked through. Remove from the skillet and set aside.
Add the remaining tablespoon of butter and the olive oil to the pan over medium-high heat.
Add the mushrooms and shallots, season with salt to taste, and cook until they begin to soften and the mushrooms have released their liquid, about 7-8 minutes.
Add the garlic and cook one more minute.
Add the marsala wine and chicken broth, and whisk to combine.
Return the chicken breasts to the pan, tucking them in the sauce. Let the mixture come to a simmer, and cook over medium heat for another 10-12 minutes, until the sauce is thickened and the chicken is cooked through.
Finally, add the heavy cream, stirring it to combine with the rest of the sauce. Cook another minute or two to let the sauce thicken a little more.
Serve the chicken topped with the mushroom marsala sauce, topped with fresh chopped parsley. Enjoy!