Combine vegetable oil and garlic in a small saucepan, add a little extra oil if necessary to cover garlic completely, and cook over low heat until very tender (25-30 minutes), then drain and set aside to cool (oil can be reserved for another use). Meanwhile, blanch parsley and tarragon until bright green (30 seconds), refresh, drain, squeeze out any excess water and finely chop. Combine in a bowl with confit garlic and 300gm of the butter, season to taste, mix to combine and set aside.
Preheat oven to 220C. Gently work your fingers or a spoon between chicken skin and flesh to loosen, working up the breasts and around the legs, being careful not to tear skin. Stuff the butter mixture evenly under the skin (any remaining can be refrigerated for 1 week for another use). Truss legs with kitchen string, place in a roasting pan, drizzle with olive oil and season to taste. Roast, basting occasionally with pan juices, until golden and juices run clear when thigh is pierced with a skewer (35-40 minutes). Transfer chicken to a plate and set aside to rest (15 minutes).
Meanwhile, place carrots in a roasting pan large enough to snugly fit in a single layer, half cover with water, chop remaining butter and scatter it over carrots along with sugar, season to taste and cover closely with a piece of baking paper. Simmer over medium heat until almost tender (4-5 minutes), remove baking paper and simmer until liquid is reduced to a glaze (1-2 minutes).
Meanwhile, for herb sauce, pound parsley, capers and anchovy using a mortar and pestle to a coarse paste. Gradually add oil, pounding to incorporate, then stir in lemon juice, season to taste and set aside.
Skim fat from roasted chicken pan juices and simmer over medium-high until a thick jus forms (3-4 minutes), then add vincotto, adjust seasoning to taste and keep warm. Carve chicken and set aside.
Toss radishes with a little herb sauce to coat and serve with warm roast chicken, glazed carrots, jus and herb sauce alongside.
This recipe is from the May 2013 issue of Australian Gourmet Traveller.