zygen.net – Green Bean Casserole

Ingredients

• 2 tbsp — butter
• 2 — or 3 yellow onions, sliced
• salt and pepper to taste
• 1 tbsp — sherry vinegar (stirred into the onions after they are caramelized)
• 2½ tbsp — flour
• 2½ cups — milk
• pinch — nutmeg
• cayenne to taste
• ¼ tsp — dried thyme
• ⅔ cup — panko
• ~2 tbsp — melted butter
• 2 lbs — green beans, trimmed, blanched
• 4 oz — grated Gruyere cheese, divided
• ⅓ cup — grated Parmesan cheese