Ingredients :

• Thick sour cream (crème fraîche) — This is what gives the sauce its identity. Use full-fat sour cream, not light — the light version will split with the heat and give you a grainy sauce. Stir it in off the heat; it’s the only step you can’t miss.
• Canned green chiles — Don’t replace these with fresh jalapeños — they are two very different things. Canned green chiles are mild and slightly smoky without the burn. They provide depth without being aggressive. You can easily find them in Mexican grocery stores or online.
• Taco seasoning — Yes, a pre-made mix. No, it’s not cheating. It contains cumin, paprika, garlic, onion, oregano — exactly what’s needed here, already balanced. Avoid low-end brands that are loaded with salt.
• Monterey Jack — An American semi-hard cheese, mild and very meltable. If you can’t find it, shredded dry mozzarella or young Gouda will do. Avoid sharp cheddar — it would overpower all the other flavors.