Soak the Roman pot and its lid in water for 10 minutes.
Wash the chicken and pat completely dry. Insert cloves into the peeled onions, distributing about 10 cloves in each onion.
Season the cavity of the chicken with salt and pepper, then stuff with the clove-studded onions.
Make a spice rub with paprika, cayenne pepper, cinnamon, and salt. Rub this all over the outside and inside of the chicken.
In a bowl, mix the liquid honey, mustard, 1 teaspoon each of cinnamon, cayenne pepper, and paprika, the balsamic vinegar, and a pinch of salt. Brush this mixture all over the chicken.
Remove the soaked Roman pot from water and pat dry. Place the chicken inside, cover with the lid, and place the pot into a cold oven. Set the oven to 225°C (437°F) and roast for 45 minutes without opening the lid.
Carefully remove the lid and return the pot to the 225°C (437°F) oven for 40–45 minutes more, basting the chicken with poultry broth every 10–15 minutes until the skin is golden and crispy (total roasting time about 1 hour 30 minutes).
While roasting, prepare the sauce: In a saucepan, heat the sugar over medium-high heat without liquid, stirring constantly until it caramelizes and turns golden brown, 5–7 minutes.
Carefully pour in the poultry broth, veal stock, and white wine (it will bubble), then add the balsamic vinegar. Bring to a simmer and reduce by half, 10–15 minutes.
Remove from heat and season with salt, pepper, cinnamon, and clove powder to taste. Whisk in cold butter until smooth and glossy.
When the chicken is done, transfer to a serving platter and let rest 5 minutes. Drain the roasting liquid into the sauce and stir to combine. Serve the chicken with the sauce.