Preheat the oven to 220°C fan.
Remove the chicken backbone using scissors and flatten the breast with your hand.
Place the bird in a roasting tin, insert garlic slices into slits, drizzle with oil, and season.
Roast for 30 minutes to color the skin.
Mix mustard, honey, chilli powder, and thyme leaves in a bowl.
Reduce oven to 180°C fan, coat chicken with the honey-mustard mix, and roast for 15 minutes.
Boil sweet potato chunks for 8 minutes until tender.
Sauté spring onions in 25g melted butter for 2 minutes.
Drain potatoes and mash with the buttery spring onion mixture.
Ensure chicken juices run clear and rest the bird under foil.
Degrease roasting tin juices and whisk in flour over low heat.
Gradually stir in 75ml wine and 500ml stock, boiling until thickened.
Carve chicken, garnish with mint and thyme, and serve with mash and gravy.