Unwrap the beef strips and chop them into bitesize pieces. Warm a large frying pan (or large pan, if you’re cooking the stew on the hob), on a medium-high heat for 2 mins, then add 1 tbsp oil and the beef. Fry for 5–6 mins, turning once or twice, till the beef is browned all over.

While the beef browns, peel and finely chop the onions. Trim the dry ends off the celery sticks and finely slice them. From this point on, follow the method either for the slow cooker or the hob.

In the slow cooker^ Scoop the beef out of the pan and add it to a 3½ ltr slow cooker. Tip in the chopped onions and celery. Trim and peel the carrots, then thickly slice them. Add them to the slow cooker too. Drop in the thyme sprigs and crumble in the beef stock cube. Pour in 500ml boiling water and season with a good pinch of salt and pepper. Pop on the lid and slow cook for 6 hrs at medium, 4-5 hrs at high or 8–10 hrs at low.

When the stew has 45 mins left, put a large pan of salted water on to boil. Peel the potatoes and chop them into small pieces. When the water is boiling, add the potatoes and simmer for 15–20 mins till they’re tender when pierced with a fork.

While the potatoes simmer, trim the roots and top 3cm off the leeks and finely slice them. Warm a frying pan over a medium-low heat for 1 min, then add 1 tbsp oil and the leeks. Season with salt and pepper and fry for 8–10 mins, stirring every so often till the leeks are soft and browned.

While the leeks are cooking, strip the soft green leaves off the kale stalks and finely slice them. Add the kale to the potatoes and simmer for 5 mins to wilt the kale leaves and finish cooking the spuds.

Drain the potatoes and kale and tip them back into the pan. Pop the pan back on a low heat and add the butter and 150ml milk. Tip in the leeks. Mash till smooth and combined. Take off the heat. Roughly chop the flat leaf parsley leaves.

Taste the stew and adjust the seasoning. Spoon the mash into 4 deep bowls and ladle over the beef stew, discarding the thyme sprigs. Garnish with the parsley and serve.

On the hob^ Scoop the beef out of the pan and pop it in a bowl. Tip the chopped onions and celery into the pan with 2 tbsp water and fry for 5 mins, stirring every so often. While the veg fry, trim and peel the carrots, then thickly slice them. Add to the pan.

Tip the beef back into the pan with any juices from the plate. Drop in the thyme sprigs and crumble in the beef stock cube. Pour in 1 ltr boiling water and season with a pinch of salt and pepper. Pop on the lid, bring to the boil, then turn the heat down and simmer for 45 mins.

While the stew simmers, put a large pan of salted water on to boil. Peel the potatoes and chop them into small pieces. When the water is boiling, add the potatoes and simmer for 15–20 mins till they’re tender when pierced with a fork. While the potatoes simmer, trim the roots and top 3cm off the leeks and finely slice them. Warm a frying pan over a medium-low heat for 1 min, then add 1 tbsp oil and the leeks. Season with salt and pepper and fry for 8–10 mins, stirring every so often, till the leeks are soft and have picked up some colour.

While the leeks are cooking, strip the soft green leaves off the kale stalks and finely slice them. Add the kale to the potatoes and simmer for 5 mins to wilt the kale leaves and finish cooking the spuds.

Drain the potatoes and kale and tip them back into the pan. Pop the pan back on a low heat and add the butter and 150ml milk. Tip in the leeks. Mash till smooth and combined. Take off the heat. Roughly chop the flat leaf parsley leaves.

Taste the stew and adjust the seasoning. Spoon the mash into 4 deep bowls and ladle over the beef stew, discarding the thyme sprigs. Garnish with the parsley and serve.