Ingredients :

• Ground beef (300 g) — Beef with at least 15% fat, not 5% — meat that is too lean dries out during cooking and loses its flavor. You can mix half beef and half ground lamb for a stronger flavor. What really counts is browning it in the pan, not just graying it.
• Potatoes (2 medium) — Waxy potatoes — a Charlotte or a Nicola. Floury varieties fall apart during cooking and make the filling pasty. Pre-cook them just enough: they should hold on a fork, not mash.
• Crème fraîche (20 cl) — Full-fat heavy cream (crème épaisse). Low-fat liquid cream creates a filling that is too fluid and won’t hold up well after baking. With heavy cream, the interior stays silky and well-bound.
• Grated cheese (100 to 150 g) — Classic Emmental or, if you want more character, hand-grated Comté. Avoid pre-shredded bags — the anti-caking starch prevents homogeneous melting and it shows in the result.