Season the chicken with some salt and pepper. Heat a large skillet over medium heat and add the olive oil. Once the oil is hot but not burning, add the chicken and sear for 3 minutes on each side. Remove from the skillet and set aside.
Using the same skillet, add the garlic and shallot and cook over medium heat for 1 minute. Add the chicken stock and wine and cook until slightly reduced, about 10 minutes. Add the sliced mushrooms and lower the heat to a simmer. Return the chicken to the skillet, cover and cook until the chicken is cooked through, an additional 10 minutes. Add the raspberries, butter, balsamic vinegar and lemon zest, and continue cooking, uncovered, for 1 minute.