Green Bean Casserole



  • 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)

White Sauce

  • 2 tbsp butter
  • 212 tbsp flour
  • 212 cups milk
  • pinch of nutmeg
  • cayenne to taste
  • 14 tsp dried thyme
  • salt and pepper to taste


  • 23 cup panko
  • ~2 tbsp melted butter


  • 2 lbs green beans, trimmed, blanched
  • salt and pepper to taste
  • 4 oz grated Gruyere cheese, divided
  • 13 cup grated Parmesan cheese



  • Cut onions french style
  • Trim green beans and cut in halves or thirds
  • Grate the cheeses
  • Melt butter and mix with panko


  • Caramelize onions
  • Make the sauce
  • Boil green beans for 3-4 minutes
  • Assemble layers in the following order
    • Half of the caramelized onions
    • All of the green beans (don’t forget to season them)
    • White sauce
    • Half the cheese
    • Rest of the onions
    • Buttered panko
    • Rest of the cheese

Full Instructions

Caramelize Onion

  • Cut off both ends of the onion
  • Cut onion in half and remove the skin
  • Cut ~14″ slices with the grain
  • Add 2 tbsp butter to a 10″ skillet over medium heat
  • Add the onions and a pinch of salt and cook, stirring occasionally, until caramelized (~15–20 mins)
  • Stir in the sherry vinegar
  • Turn off heat and reserve until needed

Make the sauce

  • Melt 2 tbsp butter in a medium saucepan
  • Add 212 tbsp flour and whisk together
  • Cook until it smells like a pie crust (~3 minutes)
  • Whisk in 212 cups milk all at once, no need to go slowly
  • Season with salt, pepper, cayenne, freshly grated nutmeg to taste, and add 14 tsp dried thyme
  • Bring to a simmer and cook another 2-3 minutes, stirring with a spatula
  • Remove from the heat and reserve until needed

Blanche the green beans

  • Wash and chop the ends off the green beans
  • Then cut them in halves or thirds
  • Bring enough water to cover the beans to a boil in a pot
  • Boil the beans just until they’re slightly soft, ~3 minutes
  • Transfer to a colander and let them fully drain

Assemble the casserole

  • Assemble in a 9x13″ casserole dish
  • Spread out half of the caramelized onions on the bottom
  • Add all of the green beans and season with salt and pepper
  • Pour white sauce evenly over the green beans
  • Spread half the cheese over the sauce
  • Add the remaining onions and press them down lightly into the sauce
  • Add buttered panko on top
  • Top with the remaining gruyere cheese
  • Finish with a layer of parmesan cheese


  • Bake at 375°F for ~30 minutes (until green beans are tender)
  • Finish with a few minutes of broiling to make the top extra crispy