Start by spatchcocking your chicken, applying a generous amount of salt on both sides, let sit for minimum an hour.
Heat up a cast iron pan (preferred), throw in the butter and oil, then the halved leeks, face down, cook for 5 minutes- until soft and caramelised. Pour in the stock, let simmer until the stock has evaporated, remove from heat and place backside up spaced out in a large, deep roasting tray.
Drizzle some olive oil over both sides of the chicken, rubbing liberally and place in the roasting tray over the leeks.
Place in the oven for 25-39 mins at 230 D for the first part of the cook
As the chicken roasts, make the tarragon cream by throwing all ingredients into a bowl and combining.
After 25-30 mins, the chicken should start to turn golden brown, remove from the oven, pour over the tarragon cream onto the chicken, add the asparagus in with the leeks and add the white wine.
Place back into the oven and turn the heat down to 145, roast for a further 35-40 mins.
Remove from the oven, rest for 10 mins, immediately serve.
