To make the hasselback potatoes, preheat the oven to 200C/180C Fan/Gas 6.

Place two wooden spoons or chopsticks on a chopping board and place a potato between them. Use a sharp knife to make cuts across the potato, cutting almost all the way through the potato (the spoons will stop you cutting all the way through). Repeat with the other potato. Place the potatoes on a baking tray and drizzle the oil all over the potatoes, getting right into the cuts. Season with salt and pepper. Bake for 30 minutes.

Meanwhile, to make the sauce, cut the top off the garlic bulb and drizzle with olive oil. Sprinkle the bulb with salt, then wrap in kitchen foil and pop in the oven, alongside the potatoes, for around 45 minutes or until softened. Leave the garlic to cool slightly.

To make the caramelised onion filling, heat the oil in a saucepan over a medium heat and fry the onions. When the onions have a little colour, mix together the sugar, vinegar and 100ml/3½fl oz water and add to the pan. Cook for around 20–30 minutes over a medium–low heat. Once golden and caramelised, remove from the heat. Leave the onions to cool.

Mix around half of the onions and the cheese together in a bowl. Reserve the remaining onions to serve.

Mix the butter and garlic well in another small bowl.

Remove the potatoes from the oven and stuff the cheese and onion mixture between each cut. Drizzle some garlic butter over each cut and return to the oven for another 20 minutes until golden. Keep warm.

To continue making the sauce, heat the oil in a saucepan over a medium heat and fry the onion until softened but not coloured.

Squeeze all of the garlic out of the bulb directly into the pan and stir it through the onions.

Add the tomato purée and paprika, then cook for 2–3 minutes until the tomato purée has darkened in colour slightly.

Deglaze the pan with the sherry vinegar and pour in the stock and tomatoes. Bring to the boil, season generously with salt and pepper and cook for 10–15 minutes until reduced and thick.

Blend the sauce with a hand blender to a smooth, rich sauce. Season with salt and pepper and keep warm.

To make the leeks, slice the leeks in half lengthwise and wash thoroughly to remove any dirt and grit from between the layers. Dry well with kitchen paper.

Heat the oil in a large frying pan until smoking hot. Place the leeks cut-side down in the pan and char until dark brown. Pour in the stock, then turn the heat down to medium–low and cover with a lid.

Cook for 5–7 minutes until tender, then season with salt and pepper.

Serve the hasselback potatoes with the sauce, reserved caramelised onions and the leeks.