Preheat your oven to 220°C/200°C fan/gas mark 7.

Remove the lamb from the fridge to allow it to come up to room temperature. Pop a saucepan of water with 1/2 tsp salt on to boil. Peel the potatoes and slice into 1cm thick rounds.

Once boiling, add the potato slices to the water and simmer until just tender, 8-12 mins. Once cooked, reserve some of the potato water (see pantry for amount), then carefully drain in a colander.

Meanwhile, trim the green beans. Peel and grate the garlic (or use a garlic press). 

Heat a drizzle of oil in a large frying pan on medium heat. Once hot, add the garlic and cook until fragrant, 30 secs. 

Add the creme fraiche, chicken stock paste and reserved potato water. Mix together, bring to the boil, then remove from the heat. Season to taste with salt and pepper. 

Lay the cooked potato slices in layers in an appropriately sized ovenproof dish, then pour over the creamy sauce. Sprinkle the cheese on top.

Bake on the top shelf of your oven until golden brown and bubbly, 15-20 mins. TIP: Put the dish onto a baking tray to catch any drips.

Pop the lamb loins onto a plate, drizzle with oil and season with salt, pepper and the dried rosemary. Use your hands to coat the meat.

Wipe out the (now empty) pan and pop on high heat with a drizzle of oil. Once hot, add the lamb to the pan and cook until browned, 2-3 mins.

Transfer the lamb to a baking tray, fat-side up, and roast on the middle shelf for 7-9 mins. TIP: This will result in medium-rare lamb. Cook for 2-3 mins longer if you want it more well done. 

Once cooked, transfer to a plate and leave to rest a couple of mins, covered loosely with foil. IMPORTANT: Wash your hands and equipment after handling raw lamb. It's cooked when browned on the outside.

While everything's in the oven, clean out the potato saucepan.

Pour the water for the jus (see pantry for amount) into the pan and bring to the boil on high heat.

Stir in the red wine jus paste, then reduce the heat to medium-high. Allow the sauce to bubble and thicken, stirring regularly, 5-6 mins. 

Once glossy and thickened, remove from the heat. Season with plenty of pepper.

Meanwhile, heat a drizzle of oil in the (now empty) frying pan on medium-high heat.

Once hot, add the green beans and stir-fry until starting to char, 2-3 mins.

Stir in the remaining garlic, turn the heat down to medium and cook for 1 min. Add a splash of water and immediately cover with a lid or some foil.

Cook until the beans are tender, 4-5 mins, then remove from the heat.

Reheat the red wine jus if needed.

Thinly slice the lamb loins and transfer to your plates. Serve with the garlicky green beans and a generous portion of gratin.

Spoon the red wine jus over the lamb to finish.

Enjoy!