Preheat the oven to 200°C.
Soak shallots in boiled water for five minutes to peel easily.
Stuff chicken with lemon and bay leaf, then season with salt, pepper, and thyme.
Melt 25g butter with oil in a casserole and brown the chicken on all sides.
Add peeled shallots and whole garlic cloves around the chicken.
Pour in vermouth and stock, bring to a simmer, then bake for 75 minutes.
Rest the chicken on a platter and skim fat from the cooking liquid.
Stir tarragon and 100ml cream into the liquid and simmer for three minutes.
Boil potato chunks in water for 15 minutes until tender.
Fry bacon and shredded kale in 25g butter for four minutes.
Add spring onions to the kale and cook for one additional minute.
Mash drained potatoes with remaining butter and 200ml warmed cream.
Incorporate the kale mixture into the mashed potatoes.
Serve carved chicken with sauce, colcannon, and baguette with soft garlic.