Put the chicken breasts in a bowl and coat in half the oil. Cut the lemon into halves. One half sprinkle over the chicken. Other half cut into round slices. Mix the 3 ingredients in the bowl. Take a baking dish and coat it with the remaining oil. Place the chicken breasts on the dish. Place one slice of lemon on each of the chicken breasts. Put the dish into an oven and cook till the chicken is white and the liquid runs clear. We don't want any pink colour to the chicken.

For the sauce, put the Butter in a skillet, add the minced garlic. cut add mushrooms and sauté till brown and the water has evaporated. Sprinkle the cornflour and coat the mushrooms. Thereafter add pepper as desired. Pour water/chicken stock and stir till the liquid thickens to have a saucy consistency.

Get the chicken onto a serving plate. Add salt if desired. I didn't. The butter in the mushroom had enough salt to uplift the whole dish. Pour the mushroom sauce on one side and viola!