Cut chicken into 1 1/2 inch pieces. Combine chicken and garlic in a skillet with wine over medium heat. When chicken is nearly cooked add broccoli and mushrooms.
In a saucepan, heat cream on medium-high setting. Bring to a simmer, but do not boil; add garlic and white pepper.
Stir corn starch into water; mix. Pour in half of the cream. Whisk, stirring in the cornstarch mixture until desired thickness is obtained. The sauce will continue to thicken gradually as it sits. Sauce must be cooked for at least 10 minutes after last corn starch is added to prevent a "powdery" uncooked taste from the corn starch. Add chicken and cheese (optional) during final 5 minutes of cooking, and serve over pasta or rice.
