Tempura spring onions with onion purée

For the onion powder, evenly spread the sliced onions in large trays and place in a dehydrator for approx. 24–48 hours until brittle and fully dried – some of the onions will go quite dark, which is great for the flavour. Place in a food processor and blitz with a small amount of sea salt. Push through a fine sieve and reserve the powder in a sealed container

To make the onion purée, add the oil to a pan and place over a low-medium heat. Add the onions to the pan and add a generous pinch of salt – this will help them to break down. Cook low and slow for approximately 45–60 minutes to give beautifully golden, sweet onions. Once cooked, transfer to a blender and blitz to a smooth purée, adding a little water if necessary to loosen it a little. Finish by blending in a pinch of xanthan gum, salt if needed, and the sherry vinegar

Prepare the spring onions by trimming the tops and the bottoms, but try not to take too much away. Wash thoroughly, then blanch for 2–3 minutes, holding the onions upright in the pan with the bulb at the bottom to ensure they cook evenly. Place straight into iced water to cool

To make the batter, whisk together all the ingredients in a bowl, stirring in enough water to give a nice, thin batter. Add the ice cubes to the batter to keep it nice and cold – at the restaurant they add crushed ice to the batter, which they add to the fryer. This makes the fryer bubble furiously, which creates a super-crispy, bubbly coating, but is definitely not advisable in a home kitchen as it might prove quite dangerous! Chilling the batter with ice cubes before coating the onions will suffice, as the colder the batter, the better

Preheat a deep-fryer or deep pan of oil to 180°C

Coat the onions in the batter and allow some to drip off – you are not looking for a thick consistency here. Place the battered onions in the fryer for approximately 90 seconds until the batter is nice and crisp. Remove from the fryer and drain on kitchen paper or a J-cloth before seasoning well with salt and the onion powder

To serve, place a few onions on each plate and add a dollop of the purée to act as a dip. Finish with a sprinkling of the onion powder to serve