Rinse the Cornish hens with water, then pat them dry with paper towels. Generously coat with salt and pepper.
Preheat the oven to 450°F (232℃). The high temperature at the beginning will crisp the skin—line the bottom of a baking pan, cast iron, or roasting pan with foil.
Use your index finger to carefully loosen the skin on top of the hens and rub them underneath the skin with garlic herb butter. Plain butter also works.
Lightly spray or coat the skin of hens with olive or cooking oil, then season with Italian and Creole seasoning.
Open up the cavity of the hens and stuff each one with the herbs, bay leaves, onion, garlic, and lemon. Just think of all those flavors infusing into the meat!
Tuck the wings under the hens and tie the legs together with kitchen twine. That helps the hens roast evenly and present well. Not doing this won't affect the taste if you don't have twine or time.
Place the hens in a roasting pan and place extra herbs, garlic, lemon, and onions around them. Roast for 20-25 minutes.
While the hen is roasting, whisk the chicken stock, white wine, and lemon juice. Set aside.
After the hens have roasted for 20-25 minutes, reduce the oven temperature to 350°F (177℃).
Baste the hen with the chicken stock mixture. Continue roasting for about 25-30 minutes or until juices run clear or an instant-read thermometer reaches 165°F (75℃). Make sure the thermometer doesn't touch the bone.
Optionally, you could use a marinade injector to inject hens with chicken mixture every 10 minutes.
Remove the pan from the oven and let the chicken rest for 5-10 minutes. Transfer fully cooked hens to a carving board and cut each one in half. Place them skin-side up on a plate.