Ingredients :

• Cooked shredded chicken — The most flexible ingredient in the recipe. A leftover roast chicken, a breast poached for 15 minutes in salted boiling water, or well-drained canned chicken. Important: shred it with a fork into long, thin fibers, not large chunks — otherwise the texture of the gratin becomes uneven and some bites will be dry.
• Canned cream of chicken soup (10.5 oz) — The workhorse of the recipe. It provides the binder, the salt, and the umami taste that ties everything together. Get the standard version, not light — the light version makes the sauce too watery during cooking. If you want to avoid it entirely, a quick béchamel with chicken broth works just fine.
• Sour cream — It adds moisture and balances the saltiness of the cream of chicken soup. Don’t skip it — without it, the gratin is too dense and slightly dry. Thick plain yogurt can substitute if you don’t have sour cream.
• Grated cheddar — Grate it yourself if you can. Pre-shredded cheddar in a bag contains anti-caking starch that prevents even melting. Mature cheddar will give more character, mild cheddar is better if you’re cooking for kids.