Put the flours and ground spices in a bowl and slowly pour in 1 cup water, stirring all the time with a wooden spoon or a whisk to make a bright yellow batter. Stir in the salt, then put to one side.

Peel strips off the cucumber with a speed peeler and put them to one side. Mix the sour cream with the cilantro and the lemon juice. Add a splash of olive oil, season, and put to one side.

Cut the leek, carrots, spring onions and red onions into thin strips – try to get them the size of long matchsticks. Mix with the chillies and ginger and set aside.

Pour the vegetable oil into a large non-stick frying pan and heat until very hot. Mix the vegetables, a little at a time, with some of the batter, add the mustard seeds and drop a tablespoon of the mix into the hot oil. Repeat with the remaining mix – you may have to fry the bhajis in batches. Press the bhajis down with the back of a fork and make sure they aren’t touching each other or they might stick together. Fry for a minute or so on each side until crispy, then drain on kitchen paper towels.

Arrange 2 or 3 bhajis on each plate with some arugula leaves and the cucumber strips, drizzle with the sour cream dressing and serve with the lemon wedges.