- 4 large baking potatoes
- 25g/1oz butter
- 3 free-range egg yolks
- 1 small onion
- 25g/1oz butter, plus extra for greasing
- 300g/10½oz button mushrooms
- 1 small bunch picked tarragon, finely chopped
- 50g/1¾oz fresh white breadcrumbs
- 75g/2½oz lamb mince
- salt and freshly ground black pepper
- 2 x 7-bone French trimmed racks of lamb
- For the duchess potatoes, preheat the oven to 200C/400F/Gas 6.
- Bake the potatoes in the oven for about 1-1¼ hours, or until tender when pierced by a knife.
- For the tarragon stuffed crown of lamb, put the onion in a food processor and pulse until very finely chopped.
- Heat a frying pan until warm, add the butter and onions and gently fry for a few minutes.
- Add the mushrooms to the food processor and blend to a really fine purée, then add them to the frying pan. Turn the heat up to high and fry for 2-3 minutes, or until all the moisture from the mushrooms has been driven off.
- Tip into a bowl with the tarragon, breadcrumbs and mince. Season generously with salt and black pepper.
- Rub some butter over a sheet of aluminium foil. Place the foil on an oven tray, buttered side up.
- Tie the two racks of lamb together to form a circle and place onto the buttered foil. Spoon the stuffing into the centre, packing down well. Place in the oven (set to 200C/400F/Gas 6) for 50-60 minutes then remove and rest for 10 minutes.
- Meanwhile, for the duchess potatoes, remove the potatoes from the oven and, when cool enough to handle, scoop out the flesh and pass it through a fine sieve into a bowl.
- Beat to a smooth and fluffy purée then add the butter and egg yolks. Season with salt and pepper.
- Spoon into a piping bag then pipe little pyramids onto a baking tray and place in the oven for 5-10 minutes, or until golden-brown.
- To serve, carve the lamb and serve with the duchess potatoes.