Ingredients :

• Mayonnaise — The base of it all. Use a creamy mayo — Hellmann’s, Duke’s, whatever — but not the light version: it’s too runny and unbalances the final texture. If you want to lighten it up, do half mayo, half plain Greek yogurt.
• Ketchup — This is what gives it the pink-orange color and the sweet-umami balance. A classic ketchup does the job perfectly, no need for a premium brand.
• Sweet pickle relish — The ingredient people tend to skip but that simply can’t be replaced. It brings the characteristic crunch and gentle acidity of real Thousand Island. Prefer the sweet version over the dill version to stay classic.
• White vinegar — One teaspoon, no more. But it’s what gives that sharp bite found in restaurant sauces that you can never replicate with lemon alone. Apple cider vinegar also works — slightly fruitier taste.