Heat the oven to 200°C. Wash and dry the potatoes, then chuck them onto a baking tray. Drizzle over one-third of the olive oil, rub it into the potatoes, season with salt and pepper, then roast for 20–25 mins until golden and cooked through.
Add the chicken breasts to a bowl with the garlic powder, onion powder and the remaining olive oil. Toss everything together, then lay the chicken on a lined baking tray and roast for 15–20 mins, until cooked through. Let it rest for a couple of minutes once done.
Meanwhile, zest the lemon. Thinly slice all of the chives. Thinly slice the celery and cucumber. Pick the parsley leaves and thinly slice the soft stems.
Chuck the cottage cheese into a blender with the chives, the parsley stems, garlic powder and onion powder. Blitz until smooth, then season with salt, pepper and a good squeeze of lemon juice. Stir through as much of the lemon zest as you like.
Finely dice the cooked chicken. Add it to a large bowl with the cottage cheese dressing, chopped celery, cucumber and half of the parsley leaves and remaining chives. Taste and adjust the seasoning with more salt, pepper, lemon juice or zest if needed.
Spoon the chicken salad onto plates with the roast potatoes on the side. Finish with a drizzle of any remaining olive oil and a scattering of the rest of the chives and parsley.
