Begin with the chicken, because everything else can happen while it marinates. In a blender or food processor, combine the sage, mint, thyme and basil with the smoked paprika, cumin, za’atar, salt, pepper, garlic, 20ml olive oil and 2–3 tablespoons of the 200g Greek yogurt, and blend to a thick, fragrant paste. In a large bowl, stir the remaining yogurt with the lemon juice and zest, then fold in the herb-spice paste until fully incorporated. Cut the thighs into 1.5-inch pieces, add them to the marinade and mix thoroughly by hand, then wash your hands and anything the raw chicken touched. Cover and refrigerate for at least 2 hours, with overnight as the target, keeping the bowl cold throughout. That long, cold rest is what lets the yogurt and lemon season and tenderise the meat all the way through.

Slice the red onions into thick rings, thick enough to keep their shape and give genuine texture rather than collapsing into slivers. In a heatproof jar or bowl, stir the boiling water, vinegar, sugar, 5g salt, coriander seeds and peppercorns until the sugar and salt have completely dissolved. Add the onion rings and press them down gently until fully submerged. Leave them at room temperature for at least 30 minutes, by which point they turn from sharp and raw-tasting to sweet, tangy and bright pink-purple, then refrigerate if holding them longer, where they keep improving. That sharp-sweet acidity is what cuts through the richness of the chicken, tzatziki and avocado.

Grate the 120g of cucumber and squeeze it with maximum force in a clean towel or your fists, because this step decides whether the tzatziki is thick and spoonable or thin and watery, and nothing can correct it afterwards. Combine the squeezed cucumber with the Greek yogurt, minced garlic, lemon juice, extra-virgin olive oil, dill, mint and 3g salt. Fold gently rather than whisking or beating, then cover and refrigerate for at least 20 minutes, or overnight if you like. It should hold its shape when spooned. That thickness is what lets the tzatziki work as both a sauce and a cooling contrast on the side of the bowl.

Start this about 10 minutes before the chicken goes on the heat. Warm the 10ml olive oil in a medium saucepan over medium-low heat, add the minced garlic and cook for 60 seconds, then add the cumin, coriander, smoked paprika and turmeric and bloom them for 30–45 seconds, stirring constantly, until intensely fragrant. Stir in the tomato paste for another 30 seconds so it caramelises slightly in the spiced oil. Pour in the 300ml chicken broth, season with salt and pepper and bring to a full boil. Remove from the heat, pour in the 300g couscous, stir once, cover tightly and leave undisturbed for 5 minutes. Fluff with a fork only, never a spoon, adding a splash of hot water and covering for 2 minutes more if any grains taste firm. Keep covered until assembly. That blooming in oil is what turns plain couscous golden and deeply savoury.

Cut the tomatoes into large, chunky cubes rather than fine dice, substantial enough to be scooped up with the chicken and couscous in one forkful. Cut the unpeeled cucumber into the same size, since the skin adds colour, texture and a slight bitterness that keeps the salad from tasting neutral. Combine in a bowl, season with salt and freshly ground black pepper to taste, drizzle with the 10ml extra-virgin olive oil and toss briefly. Leave it to rest while you cook, but serve within 2 hours of making it. That salt is what draws a little tomato juice out to mix with the oil into a simple, natural dressing.

Make this last, in the final minutes before assembly while the cooked skewers are resting, so the flesh stays green. Halve the avocado, remove the stone and cut the flesh into cube-sized chunks while it is still in the skin, then scoop the pieces out carefully with a large spoon. Season directly with salt and freshly ground black pepper to taste. The cubes should match the size of the tomato and cucumber so the three sit together neatly in the bowl. That seasoning is what keeps the avocado from tasting flat beside the bold chicken and sharp onion.

While the couscous steams, take the marinated chicken from the refrigerator and heat your grill, grill pan, cast-iron pan or carbon-steel pan until screaming hot, with at least 3–4 minutes of preheating. Thread the pieces onto skewers without over-packing them, about 2–3 skewers per bowl, and do not wipe off the marinade, because the yogurt coating is what builds the char and crust. Cook the first side undisturbed for 3–4 minutes until deep golden-brown, flip and cook the second side for another 3–4 minutes. Continue cooking until the thickest piece of chicken reaches at least 74°C (165°F) on an instant-read thermometer, because the stated minutes are estimates, not substitutes for checking internal temperature. Cook in batches if using a pan, discard any leftover marinade, then rest all the skewers for 5 minutes on a clean plate. That temperature check is what makes the char safe to enjoy.

Spoon a generous portion of couscous onto one side of each bowl as the grain base, then lean 2–3 skewers across the centre, resting against the couscous. Spoon a generous mound of tzatziki on the opposite side of the chicken so it looks abundant rather than like a drizzle. Add the tomato-cucumber salad in a section next to the tzatziki, place the avocado cubes in their own section alongside the couscous, and lay a portion of the pickled red onion rings in the remaining space. Scatter the parsley or cilantro very generously over the entire surface. That heavy herb finish is as much a visual element as a flavour one.