Preheat oven to 400 degrees. Season inside and out of cornish hens. In a bowl combine mushrooms, onions, carrots, peas, 1 tablespoon olive oil, and salt and pepper to taste. Stuff vegetables into cavity of each bird to full capacity. Drizzle hens with remaining oil. Criss-cross 2 bacon slices across each hen, tucking ends under birds to keep in place. Place hens on a roasting rack in a roasting pan and pour chicken stock in bottom of pan. Roast hens 45 minutes to 1 hour or until an instant reading thermometer inserted in thickest part registers 170 degrees. Allow hens to rest, loosely covered with foil, for at least 10 minutes while you finish sauce. Bring sauce to a boil in roasting pan, scraping bottom of pan to incorporate any drippings; season to taste with salt and pepper. To serve, drizzle hens with sauce.