Ingredients:

  • 25 lb Fresh Haricots Verts (or French Green Beans), Trimmed and washed
  • 1 Tbsp Kosher Salt, For blanching water
  • 4 Tbsp Unsalted Butter, Divided (2 Tbsp for mushrooms, 2 Tbsp for roux)
  • 1 large Shallots or Yellow Onion, Finely diced
  • 10 oz Cremini Mushrooms (Chestnut), Sliced thinly
  • 3 Tbsp All-Purpose Flour, For the roux
  • 1 cup Chicken or Vegetable Stock (low sodium), Warm
  • 1 cup Whole Milk or Half-and-Half, Warm, full fat recommended
  • 1 tsp Garlic Powder
  • 1/2 tsp Dried Thyme
  • Pinch Freshly Grated Nutmeg
  • 1 tsp Worcestershire Sauce
  • Black Pepper, To taste
  • 8 oz can Crispy Fried Onions (High-quality store-bought)

Instructions:

  1. Prepare the Water: Bring a large pot of water to a rolling boil. Add 1 tablespoon of salt. Prepare a large bowl of ice water nearby (the 'shocking' bath).
  2. Blanch the Beans: Drop the trimmed green beans into the boiling water. Cook for 3–4 minutes until they are bright green and tender-crisp (al dente).
  3. Shock and Drain: Immediately scoop the beans out of the boiling water and plunge them straight into the ice bath. This stops the cooking process and locks in the vibrant colour. Drain well and set aside.
  4. Sauté Aromatics: Melt 2 Tbsp of butter in the large skillet over medium heat. Add diced shallots (or onion) and sauté until softened, about 3 minutes.
  5. Cook Mushrooms: Add the sliced cremini mushrooms. Sauté until they have released their liquid and are deeply browned and tender (about 8–10 minutes). Season with salt, pepper, garlic powder, and thyme. Remove mushrooms and shallots from the skillet and set aside.
  6. Make the Roux: Melt the remaining 2 Tbsp of butter in the same skillet. Whisk in the flour until a smooth paste (the roux) forms. Cook for 1–2 minutes, stirring constantly, until the roux smells slightly nutty.
  7. Whisk in Liquid: Slowly whisk in the warm stock until fully incorporated and smooth. Then, gradually whisk in the warm milk or half-and-half.
  8. Simmer and Thicken: Bring the mixture to a gentle simmer, whisking constantly, until the sauce coats the back of a spoon thickly (4–5 minutes).
  9. Season the Sauce: Reduce the heat to low. Stir in the Worcestershire sauce and a pinch of nutmeg. Return the sautéed mushrooms and shallots to the sauce. Taste and adjust seasoning as necessary.
  10. Preheat and Combine: Preheat oven to 375°F (190°C). Gently fold the blanched green beans into the creamy béchamel sauce until evenly coated.
  11. Transfer: Pour the mixture into the prepared 9x13 inch casserole dish.
  12. Initial Bake: Bake for 15 minutes, or until the sauce is bubbly around the edges.
  13. Add Topping: Remove the casserole from the oven. Evenly sprinkle the crispy fried onions over the top.
  14. Finish Baking: Return to the oven for a final 5–10 minutes, or until the onions are golden brown and the sauce is hot throughout.
  15. Serve: Let rest for 5 minutes before serving.