Loin of Lamb in Crisp Potato Crust With Pea and Mint Purée and Tarragon Jus
I’ve got Lea Linster to thank for this dish. It can be prepared well in advance as, once wrapped in the potato crust, the lamb will sit happily for an hour or two before roasting. Don’t be worried by how small the lamb loins appear after being trimmed down – each piece might end up weighing no more than 200g (7 oz). The best way to make dried white breadcrumbs for the crust is to toast some bread and simply blitz in a food processor
For the lamb
- 1 large baking potato, peeled - about 374g(13oz)
- 5 tsp olive oil
- 3 tsp chopped flat-leaf parsley
- 2 tbsp dried white breadcrumbs (see recipe introduction)
- 2 x 450g (1 lb) boneless loins of lamb, completely trimmed of fat
- Salt and freshly ground black pepper
- Sprigs of mint, to garnish
For the tarragon jus
- 50ml (2fl oz) balsamic vinegar
- 200ml (7fl oz) Madeira Sauce (see recipe below)
- 1 tsp tomato purée
- 1 tsp light muscovado sugar
- 1 tbsp chopped tarragon leaves
For the pea and mint purée
- 4 tbsp double cream
- 1 tbsp chopped mint
- 225g (8 oz) fresh or frozen peas
- 1 tbsp butter at room temperature2 tbsp milk
Preheat the oven to 200ºC (400ºF), gas mark 6. Cut the potato into long, thin strips (julienne) using either a mandolin, the coleslaw blade of your food processor, or by hand. Pile the strips into the centre of a clean tea towel and squeeze out all of the excess water.
Heat 2 teaspoons of the olive oil in an 18cm (7 in) frying pan over a high heat. Reduce the heat a little, sprinkle over half the potato strips in a thin, even layer, and press down the crust as it cooks for about 3-4 minutes until crisp and golden on the bottom, leaving the top of the potato crust uncooked. Slide out of the saucepan crispy-side down, on to a clean tea towel. Repeat with another 2 teaspoons of oil and the remaining potato. Sprinkle the uncooked side of the potato crusts with the parsley.
Place the dried breadcrumbs on a flat plate. Season the trimmed lamb loins well with salt and pepper and then roll each piece in the dried breadcrumbs to evenly coat it all over. Place one loin at the end of each potato crust. Roll up like a Swiss roll, using the tea towel to lift it up and over, while squeezing the potato tightly around the lamb, so that it sticks to it and completely encloses it.
Use the remaining teaspoon of olive oil to grease a wire rack set in a roasting tin. Transfer the lamb onto the rack, seam-side down (the potato crust stays more crispy that way). Bake for 20-25 minutes for medium or longer if you prefer your meat well-done.
Meanwhile, to make the tarragon jus, heat a medium-sized saucepan until quite hot. Add the balsamic vinegar, and as soon as it stops bubbling, add the Madeira Sauce, tomato purée, sugar and tarragon and boil for about 5 minutes until it is reduced by three-quarters and well flavoured. Season with salt and pepper and keep warm over a low heat.
To make the pea purée, place the cream and milk in a medium-sized saucepan with the mint and bring to the boil. Add the peas and butter and cook for 2 minutes (or 4 minutes if the peas are frozen). Season the pea mixture with salt and pepper to taste and then transfer to a food processor. Whiz until well blended to a smooth purée, then pass through a sieve into a clean saucepan and reheat gently. Keep warm over a low heat.
Remove the lamb from the oven and allow to rest, uncovered, on kitchen paper for 5 minutes. Then cut each piece of lamb into four thick slices. Arrange two pieces of lamb on each warmed plate and garnish with fresh mint. Serve with a spoonful of the pea purée alongside and a drizzle of the tarragon jus.
This has to be one of the nicest sauces that we use in the restaurant. It’s a vital element of my signature lamb recipe above. It keeps for up to three days in the fridge if stored in a rigid plastic container, and it also freezes well.
Makes 200m (7 fl oz)
- 1 tbsp balsamic vinegar
- 1 tbsp light muscovado sugar
- 200ml (7 fl oz) Madeira
- 100ml (3½fl oz) red wine
- 600ml (1 pint) beef stock
- 1 tsp chopped thyme leaves
- Salt and freshly-ground black pepper
Pour the balsamic vinegar into a small saucepan and stir in the sugar. Bring to the boil, then reduce to a simmer, and cook over a medium heat for about 2 minutes or until the vinegar and sugar are reduced to a syrup. Add the Madeira and red wine and return to a simmer for about 6-8 minutes until the sauce has reduced by half.
Add the beef stock and thyme to the sauce and reduce it again for about 20 minutes until the sauce is thick and glossy and has become more concentrated in flavour.
Season the sauce with salt and pepper to taste. Use immediately or cool and store in the fridge or freezer in a lidded plastic container.