Drain the cottage cheese: Line a fine-mesh strainer with a paper towel or coffee filter and set it over a bowl. Add 200 grams fat-free cottage cheese and refrigerate for 20–30 minutes. You'll lose 30–50g of whey — that's the point. Non-negotiable with fat-free; skip it and the dressing will be watery.
Tame the yellow onion: While the cheese drains: mince 2 tablespoons yellow onion, minced and submerge in cold water for 10 minutes. This pulls out the sulfurous bite. Drain and pat dry before using.
Blend the dressing: Add the drained 200 grams fat-free cottage cheese, 1.5 tablespoons Dijon mustard, 1 tablespoons fresh lemon juice, 2 teaspoons dried dill, and a pinch each of 0.5 teaspoons kosher salt and 0.3 teaspoons freshly ground black pepper to a food processor or high-speed blender. Run 30–60 seconds until completely smooth and glossy. Then drizzle in 1 teaspoons olive oil and pulse briefly to incorporate. The dried dill rehydrates in the wet dressing during blending.
Prep the chicken and aromatics: Shred or roughly chop 500 grams smoked chicken thigh meat, skin removed into bite-sized pieces. Finely dice 2 celery stalks, finely diced. Combine with the drained onion in a large bowl.
Combine and season: Fold the blended dressing into the chicken mixture until evenly coated. Season with 0.3 teaspoons smoked paprika, 0.3 teaspoons garlic powder, remaining 0.5 teaspoons kosher salt, and 0.3 teaspoons freshly ground black pepper. Taste and adjust — smoked thigh varies in salt from the brine.
Chill: Cover and refrigerate at least 30 minutes so the flavors meld and the dressing tightens further. 60+ minutes is better. Overnight is best.