In a shallow bowl, combine the flour, salt, and pepper. Coat each piece of chicken in the flour mixture, shaking off the excess flour.
In a large pan over medium heat, add the oil. Add the chicken and cook about 8-10 minutes, flipping halfway through, until golden on the outside. Transfer the chicken to a plate and cover with aluminum foil to keep warm.
In the same pan over medium heat, add the mushrooms, shallots, sage, and ¼ cup water, season with salt and pepper, cooking about 3-5 minutes, until the mushrooms are tender, stirring frequently. Stir in the wine and cream, simmering over medium-high heat for another 3-5 minutes, until slightly thickened. Remove from heat and stir in the butter. Top the chicken with mushroom sauce and sage.