Ingredients:

  • 2 large Yellow Onions (or 4 large Shallots), thinly sliced (approx. 400g)
  • 120 ml (½ cup) Buttermilk
  • 120 g (1 cup) All-Purpose Flour
  • 5 g (1 tsp) Fine Sea Salt
  • Vegetable or Canola Oil, for frying (approx. 700 ml)
  • 900 g (2 lbs) Fresh Green Beans, trimmed
  • Water and Ice Bath
  • Pinch of Salt
  • 55 g (4 Tbsp or ½ stick) Unsalted Butter
  • 225 g (8 oz) Cremini Mushrooms, cleaned and finely sliced
  • 3 cloves Garlic, minced
  • 55 g (½ cup) All-Purpose Flour
  • 480 ml (2 cups) Chicken or Vegetable Stock (low sodium)
  • 240 ml (1 cup) Whole Milk or Half-and-Half
  • 5 g (1 tsp) Fresh Thyme Leaves
  • 3 ml (½ tsp) Worcestershire Sauce (optional)
  • Pinch of freshly grated Nutmeg
  • 10 g (2 tsp) Fine Sea Salt
  • 2 g (½ tsp) Freshly Ground Black Pepper

Instructions:

  1. Prep Onions: Thinly slice the onions/shallots. Place them in a bowl with buttermilk and soak for at least 10 minutes.
  2. Prep Beans: Bring a large pot of salted water to a rolling boil. Prepare an ice bath.
  3. Blanch: Drop the trimmed green beans into the boiling water for 3–4 minutes until bright green and tender-crisp. Immediately plunge them into the ice bath to stop the cooking. Drain thoroughly.
  4. Coat Onions: Drain the onions from the buttermilk (do not rinse). Toss them with the flour and salt mixture until fully coated, separating any clumps.
  5. Heat Oil: Pour oil into the skillet/Dutch oven to a depth of about 2.5 cm (1 inch). Heat the oil to 175°C (350°F). Use a thermometer.
  6. Fry: Working in batches, carefully drop the coated onions into the hot oil. Fry for 3–5 minutes, stirring occasionally, until deeply golden brown and crispy.
  7. Drain: Remove the onions immediately with a slotted spoon and transfer them to a wire rack lined with paper towels. Season immediately with a small pinch of salt. Let them cool completely.
  8. Sauté Mushrooms: Preheat oven to 190°C (375°F). In a large saucepan, melt the butter over medium heat. Add the sliced mushrooms and sauté until they have released their liquid and browned beautifully (about 8–10 minutes).
  9. Aromatics: Add the minced garlic and thyme; cook for 1 minute until fragrant.
  10. Make the Roux: Sprinkle the flour over the mushroom mixture. Stir continuously for 1–2 minutes to cook out the raw flour taste.
  11. Add Liquids: Slowly whisk in the stock until smooth, followed by the milk/half-and-half. Bring the mixture to a simmer, whisking constantly.
  12. Thicken and Season: Once the sauce thickens to coat the back of a spoon (3–5 minutes), remove from heat. Stir in the Worcestershire sauce, nutmeg, salt, and pepper. Taste and adjust seasoning.
  13. Combine: Gently fold the blanched green beans into the mushroom sauce until fully coated.
  14. Assemble: Pour the mixture into the prepared 9x13 inch baking dish.
  15. Initial Bake: Top the casserole with half of the crispy fried onions.
  16. Bake: Bake in the preheated oven at 190°C (375°F) for 15 minutes, or until the sauce is bubbly and the topping is lightly browned.
  17. Finish: Remove from the oven. Immediately sprinkle the remaining half of the crispy fried onions evenly over the top. Serve piping hot.