Preheat oven to 325º F.
Using a very sharp knife, carefully slice the chicken breasts in half using a horizontal cut.
Place 2 chicken breast halves into a Ziploc bag, remove air and seal.
Using a meat mallet or rolling pin, gently pound the chicken until it’s an even thickness, about ⅛-1/4 inch. Do the same with the remaining chicken breasts.
In a separate Ziploc bag, mix the flour, salt and pepper. Add the chicken a few pieces at a time; seal the bag and shake until all the chicken has been floured. Remove chicken; shake off excess flour and set side.
Heat half of the butter and half of the oil in a large nonstick skillet over medium heat. To flavor the butter/oil mixture, saute the garlic cloves in the butter and oil until lightly brown. Remove the garlic (or if you want to, you can just leave the garlic in).
In the same pan, cook the chicken pieces over medium heat until lightly browned on both sides, 2-3 minutes per side. Add more butter and oil if needed.
Remove the chicken to an 9" x 13" baking dish. Cover and keep warm.
Add the remaining butter and oil to the pan. Cook and sauté the mushrooms in the same skillet as the chicken until the mushrooms have turned brown at the edges and have absorbed the butter and oil.
Arrange mushrooms over the chicken pieces.
Add the wine, lemon juice and broth to the skillet. Bring liquids to a boil.
Pour the sauce over the chicken and mushrooms.
Bake at 325º F, covered tightly, for 45 minutes to 1 hour.
Garnish with chopped fresh parsley and sliced lemons before serving.