• Preheat oven to 400°F/200°C with the rack in the center of the oven.
  

For the herb butter:

• To a bowl, add the softened butter, rosemary, sage, parsley, salt and pepper, mix well.

For the turkey:

• Dry the outside of your turkey breast.
  
• Lift the skin of the turkey breast and spread some of the butter between the meat and the skin. Spread the rest of the butter all over the turkey. Wash your hands well after handling raw meat.
• To the bottom of your roasting dish, add the carrots, celery, parsnips, garlic, onion and bay leaf in an even layer, pour the warm chicken stock. Lay the turkey breast, skin-side up on top of the vegetables.
• Roast for 45 minutes, turn down the heat to 350°F/177°C, then continue to roast for a further 20-30 minutes. The duration of last part of roasting will depend on how hot your oven runs. Check the internal temperature with a meat thermometer and remove from the oven when the temperature at the thickest part of the meat is 162-165°F. It will continue to cook when resting.
  
• Take the turkey breast out of the pan and set on a cutting board, cover lightly with foil. Remove the vegetables and add to an oven-proof dish put them back in the oven (turned to very low) to keep warm.
  
• Strain the turkey drippings into a small saucepan and add more stock to make 1 cup (236 ml) if needed.
  
• Sprinkle flour or cornstarch into a small bowl and whisk in a little chicken stock until there are no lumps. Bring the turkey drippings to a simmer and slowly add the flour mix while whisking. Simmer until thickened, taste for salt.
  
• Slice the turkey and serve with the gravy and your favorite sides.