Ingredients:

  • 3 large shallots, thinly sliced (Approx. 200 g)
  • 1/4 cup All-Purpose Flour (30 g), for coating
  • 2 cups Neutral Oil (500 ml), for shallow frying
  • 1/2 teaspoon Sea Salt (3 g)
  • 1 1/2 pounds Fresh Green Beans (680 g), trimmed
  • Water and Ice, as needed for blanching
  • 4 tablespoons Unsalted Butter (56 g), divided
  • 8 ounces sliced Cremini Mushrooms (225 g)
  • 2 cloves minced Garlic (10 g)
  • 1/4 cup All-Purpose Flour (30 g), for the roux
  • 1/2 cup low sodium Chicken or Vegetable Stock (120 ml)
  • 1 1/2 cups Whole Milk (360 ml)
  • 1/2 cup Heavy Cream (120 ml)
  • 1 teaspoon Fresh Thyme Leaves (2 g)
  • Kosher Salt and Freshly Ground Black Pepper, to taste
  • Pinch freshly grated Nutmeg
  • 1/2 cup finely grated Parmesan Cheese (50 g), optional

Instructions:

  1. Prepare the Shallots (If making homemade): Slice shallots thinly. Toss lightly with the 1/4 cup flour and salt.
  2. Fry the Shallots: Heat neutral oil in a deep skillet to 350°F (175°C). Fry shallots in batches until deep golden brown and crisp (2-3 minutes per batch). Do not overcrowd.
  3. Drain and Cool: Remove shallots with a slotted spoon and drain thoroughly on paper towels. Season immediately with a tiny extra pinch of salt. Set aside.
  4. Prep the Beans: Bring a large pot of salted water to a rolling boil. Prepare an ice bath. Blanch the trimmed green beans for 3–4 minutes until bright green and tender-crisp (al dente). Immediately transfer beans to the ice bath to halt cooking. Drain well.
  5. Sauté Mushrooms: Melt 2 tablespoons of butter in the saucepan over medium-high heat. Add sliced mushrooms and sauté until they have released their liquid and browned nicely (about 5–7 minutes). Stir in minced garlic and thyme; cook for 1 minute until fragrant. Remove mushrooms and garlic from the pan and set aside.
  6. Start the Roux: Reduce heat to medium-low. Add the remaining 2 tablespoons of butter to the saucepan. When melted, whisk in the 1/4 cup of flour. Cook the roux for 2 minutes, stirring constantly, until smooth and pale golden (a 'blond roux').
  7. Create the Sauce: Slowly whisk in the warm stock until fully incorporated and smooth. Then, gradually whisk in the warm milk and heavy cream. (Tip: Warm liquids prevent lumps and speed up the thickening process.)
  8. Simmer and Season: Bring the sauce to a gentle simmer, whisking occasionally. Reduce heat to low and cook until the sauce coats the back of a spoon (about 5 minutes). Stir in salt, pepper, a pinch of nutmeg, and Parmesan cheese (if using). Taste and adjust seasoning aggressively.
  9. Combine: Fold the reserved sautéed mushrooms and blanched green beans into the béchamel.
  10. Assemble: Pour the green bean mixture into the prepared 9x13 casserole dish. Preheat oven to 375°F (190°C).
  11. Initial Bake: Bake at 375°F (190°C) for 15 minutes, or until bubbling slightly around the edges.
  12. Add Topping: Remove the casserole from the oven. Gently scatter the crispy shallots over the top.
  13. Final Bake: Return to the oven for an additional 5–10 minutes, just until the topping is warm and the sauce is fully heated through.
  14. Rest and Serve: Let the casserole rest for 5–10 minutes before serving. This allows the sauce to settle.