Place a roasting tin in the oven at 220C/425F/Gas 7 to heat up. When the oven is heated, place the duck crown in the tin, skin side down and cook for 14 minutes. Take out of the oven and rest on rack for 10-15 minutes.
Meanwhile, sweat the vegetables, apple, herbs and garlic in a large frying pan until soft and golden in colour.
Add the apple juice and reduce in volume by half.
Add stock and reduce by half again.
Whisk in the butter and season to taste.
Slice the duck thinly and serve with Summer Turnips, Cider Potatoes and scattered Caramelised Granny Smiths.