Place chicken breasts in a large ziplock freezer bag (or between two pieces of plastic wrap) and using a mallet or rolling pin pound the chicken until its about 1/2 inch thick. Sprinkle with salt and pepper.
Add red onion and garlic and saute for about 30 seconds then add chicken broth. Reduce the heat to low and simmer 10 minutes or until reduced by half.
Add in butter, and heavy cream whisk until combined. Add chicken breasts back in and simmer on low another 3-4 minutes.
Garnish with fresh chopped parsley