Preheat the oven to 425 °F.
Layer the vegetables In the Dutch oven, add the veggies - carrots, celery, shallots, and garlic halves.
Drizzle the oil over them. Then, season with salt and pepper.
Add the sprigs of rosemary and thyme.
Brush the surfaces of the vegetables with the lemon-mustard glaze, especially the garlic halves and the outer edges of the vegetables.
Season the chicken generously with salt and pepper - outside as well as inside the cavity
Fill the cavity with slices of onions, garlic, and lemon.
Truss the chicken by tying the legs together.
Place the chicken on the vegetable bed breast-side up. Brush the chicken with the remaining glaze.
Double-check the roasting time, which is by weight. You will roast for 15 minutes at 425 ° F. Then, reduce the oven temperature to 360 ° F - don’t open the oven. Roast for an additional 20 minutes per pound depending on the weight of the chicken. For a 3 ½ pound chicken (assume the giblets weigh ¼ pound and subtract that) that is an additional 3.25 x 20 = 65 more minutes for a total of 80 minutes of roasting. When roasting is complete, the juices should run clear when you pull on the leg of the chicken. The safest strategy is to invest in an oven thermometer and roast until the internal temperature of the chicken is 165 ° F.
Remove the chicken from the oven and cover it with the lid of the Dutch oven or tent it with a foil – let cool for at least 15 to 20 minutes before you carve to keep the juices from flowing away from the meat. Serve with the veggies and use any pan dripping to make gravy.
To keep the chicken warm in case it’s ready before guests are, place the cover on the Dutch oven and set the temperature of the oven at 250 F. A little more pan juices will accumulate in the bottom of the pan if you do this, but the chicken will stay warm without drying out - you can keep it warm like this for up to 1 hour.
Carve and serve the meats your family prefers. Mine always likes the white meat for the first meal. Then I debone the carcass and refrigerate the meat while I simmer the bones for bone broth.