Heat the oven. Preheat to 220°C / 200°C fan / 425°F and line a large baking tray with parchment.
Prep the fries. Cut the sweet potatoes into 1cm-thick fries. Toss in a bowl with the cornflour first, then add the olive oil, paprika, cumin, garlic powder and salt. Spread out in a single layer on the tray — give them space, no overlapping.
Roast. Bake for 20–25 minutes, flipping once halfway through, until deep gold and crisp at the edges.
Pickle & make the salsa in parallel. While the fries roast, combine the onion, vinegar, sugar and salt in a small bowl — leave to pickle. In another bowl, mix the diced tomato, cucumber, parsley, olive oil, lemon and seasoning.
Whisk the tahini drizzle. Stir the tahini with the lemon juice and garlic — it’ll seize, that’s normal. Add cold water a tablespoon at a time, whisking, until you have a pourable cream. Season with salt.
Cook the shawarma. A few minutes before the fries are done, heat the oil in a non-stick pan over medium-high heat. Add the Vivera shawarma strips and fry for 5–7 minutes, tossing often, until crisp and deeply golden.
Load & serve. Pile the hot fries onto plates. Top with the shawarma, then spoon over the tomato salad and pickled onions. Drizzle generously with tahini sauce, scatter with parsley, and tuck pickled chillies and olives in at the side. Eat immediately, with extra lemon to squeeze over.