Preheat oven to 375 degrees.
Place the butter and oil in a large saute pan over medium heat. Wait for the butter to melt, then whisk the oil and butter together in the pan. Place the chicken breasts in the pan and saute until golden brown on both sides. Transfer the chicken breasts to a 9x13 inch baking dish or an ovenproof skillet large enough to hold 8 chicken thighs.
Place the cream, chicken broth, lemon juice and zest, garlic powder, Parmesan cheese salt, and pepper together in a medium size saucepan, whisk to combine . Simmer for 10 minutes. Combine the water and cornstarch, stir to combine. Whisk it into the sauce, cook until slightly thickened. Remove from the heat. Pour the sauce over the chicken thighs and bake at 375 degrees for 25 -30 minutes or until thighs are cooked through.