The easy way to roast lamb | Back to Basics

Preparing a roast dinner is what you've told us makes most of you most nervous. But it needn't be a nightmare of multitasking if you follow these simple steps - starting with this delicious, seasonal roast lamb
When Jane and I were first asked to do this column, we put out a summons on Twitter asking nervous and beginner cooks to tell us which dishes they were most frightened of attempting. The answer was near-unanimous: a roast dinner.They gave two main reasons for this. First up: multitasking. A roast is usually the centrepiece of a social occasion, even if it's just Sunday lunch for the family. The thought of entertaining guests at the same time as balancing the battery of trays and pans required - like a culinary version of the Cat in the Hat - is understandably daunting. This leads us to the second worry: timing. When the multi-tasking goes wrong, it is easy to overcook the meat and end up serving boot leather. Or you might err in the other direction, undercook the beast, and kill off your guests with food poisoning.But fear no more. This week's recipe is intended to help you master the juggling act and land your roast triumphantly on the table.It's a one-pot roast, which drastically reduces the tower of pans. The potatoes go in with the lamb and cook in its juices. All you need to serve with it is the green sauce (see below), which is easier than a homemade mint sauce but complements the meat just as well. This you can make in the morning, or even a couple of days before; and a green vegetable. A brassica is ideal - cabbage, spring greens or broccoli.Chop up your greens before you start making the roast, to avoid last-minute fussing. Then, while the roast is resting (after step five), boil it in a pan until it is just fractionally overdone (this will take 10 minutes or so). This way, when you dress it with butter (or olive oil) and a dash of soy sauce, the softer veg will absorb the salty, savoury, fatty dressing in a most unctuous way.As I have mentioned before in this column, there are two ways to cook meat: hot and fast, or low and slow. Anything inbetween is liable to end in toughness. This recipe uses the fast timing to give you a lovely red and juicy leg of lamb, but you can also do it long and slow, so that it falls off the bone. The alternative timing is at the bottom of the recipe. It's worth trying both methods: the results, though very different, are so good it's hard to choose between them. If you want to use a meat thermometer, there are directions on how to use it here.Finally, a word on food poisoning. It is almost impossible these days to poison people if you use fresh meat and the outside of it is cooked through. Relax. (Except with chicken, which must always be cooked right through.)And for pudding? I recommend shop‑bought vanilla ice-cream with my wife's Mars-Bar sauce (Mars Bars melted in a splosh of milk). You'll never be nervous of Sunday lunch again.

Roast lamb

This recipe will give you lovely pink meat and juice-infused potatoes.Prep time 20 minutesCooking time 1 hourServes 6
1.5kg leg of lamb
3 garlic cloves, crushed
3 sprigs rosemary leaves, finely chopped
1 tbsp olive oil
Juice ½ a lemon
1kg potatoes
2 onions
1 tbsp olive oil
250ml chicken stock
Salt and black pepper1 Preheat the oven to 210C/425F/gas mark 7. Prepare the lamb. Make sure you remove the leg from the fridge at least an hour before cooking so it can come up to room temperature. Make slashes 1-2cm deep all over the lamb leg with a sharp-pointed knife. If possible, loosen the meat away from the bone at the thickest part of the leg.2 In a bowl, mix the crushed garlic with the rosemary, a good grind of black pepper, the olive oil and lemon juice to make a paste.3 Push the paste into the slashes in the lamb leg. Make sure you use all the paste.4 Peel and thinly slice the potatoes and onions. Toss in a bowl with salt and pepper and a little olive oil. Place in the base of a roasting tray in which the lamb can fit so you have a thin layer. Pour the chicken stock on top.5 Place the lamb on the potatoes and pop into the hot oven for 30 minutes. Turn the oven down to 190C/375F/gas mark 5 for a further 30 minutes. Remove the lamb from the oven and wrap in foil. Allow it to rest for at least 30 minutes. These timings result in pink meat; add another 20 minutes per kg if your leg is larger than the one used here.Recipe by Jane Baxter

What else you can do

Try inserting tinned anchovies into the lamb meat, along with butter and rosemary. Use a small knife to stab little holes in the meat, then slip an anchovy into each hole. Drizzle with balsamic vinegar before roasting to give the skin a caramelised tang.This is a "fast cook" recipe - the alternative is to cook the joint very slowly on a low temperature for a longer time - 160C/325F/gas mark 3 for 4 hours (you can turn the heat down to 120C/250F/gas mark ½ after this and leave it for a couple more hours without harming it).

For showing off

Mix the potatoes with a paste made from:
2 tbsp chopped tinned tomatoes
2 tbsp chopped parsley
4 cloves garlic crushed
2 tbsp grated parmesan (or pecorino)1 Massage the potatoes with olive oil, top with lamb and then cook as directed above.

Green sauce (or salsa verde)

You can make this well in advance. You get a slightly better texture if you pound it in a pestle and mortar, or chop it fine with a knife and then stir in the liquids, but it is still delicious made in a blender. Don't let the purists bully you. You can omit the anchovies if you need to, but they do give a rich depth. You could also use substitute these green herbs for whatever else takes you fancy. Basil and tarragon are both lovely.Prep time: 5 minutesMakes 1 jar
20g fresh mint
20g flat-leaf parsley
1 tbsp capers
2 tsp dijon mustard
4 anchovy fillets
Salt and black pepper
200ml extra virgin olive oil
Juice of ½ a lemon1 Put all the ingredients into the blender and blend until smooth. It should be runny, but substantial. Put into a sealable jar and pop into the fridge.Henry Dimbleby is co-founder of the natural fast-food restaurant chain Leon (@henry_leon). Get your kids cooking at cook5.co.uk
Photo: Rub the joint with the garlic and rosemary, forcing the crushed cloves into the slits made in the meat. Photography: Jill Mead for the Guardian