Using a food processor with a grating insert or a box grater, grate the washed, unpeeled potatoes and transfer to a large bowl of very cold water. Grate the onion into a bowl.

Scoop the grated potatoes out of the water using your hands, shaking off the excess water, and put the potato and onion on a clean, dry tea towel or muslin cloth. Thoroughly wring out the excess liquid over the bowl of water, reserving the liquid. You want the mixture to be as dry as possible.

Transfer the potato and onion mixture to a large, dry bowl and add the egg, matzo meal, 1 tsp salt, 1/2 tsp ground black pepper, the za’atar and most of the herbs. Carefully pour out the potato water from the bowl, keeping the white potato starch that will have sunk to the bottom. Add the starch to the grated potato mixture and stir thoroughly to combine.

Pour about 1 1/2cm depth of oil into a large frying pan, and set it over a medium heat. Allow it to get hot — a cube of bread should turn golden in a minute. Scoop heaped tablespoons of potato mixture from the bowl and press down firmly to release any more water. Flatten and carefully add to the pan, about 2cm apart. Do not overcrowd the pan or the temperature of the oil will drop.

Flatten the latkes again with a fish slice and leave to cook until crisp and dark golden underneath – about 4-5 mins, then turn them over. Cook for a further 4-5 mins until both sides are golden brown, and the potato and onion are cooked through.

Transfer the latkes to plates or baking sheets lined with kitchen paper and sprinkle with a little salt. If you are making a large batch, keep them warm in a low oven. Repeat until all the mixture is used up. You may need to top up the oil during the cooking process.

To make the lemon tahini sauce, mix the tahini, yogurt and lemon juice in a small bowl. As you stir, it will thicken up and become gluey. Gradually add cold water, a teaspoon at a time, stirring after each addition, until you have a pouring consistency. Season to taste and serve the latkes drizzled with the sauce.