Ingredients:

  • 2 large shallots, thinly sliced
  • 1 cup vegetable oil (for frying)
  • Pinch of salt
  • 5 lbs fresh green beans, trimmed (or 2 cans, drained and rinsed)
  • 4 Tbsp unsalted butter
  • 4 Tbsp all-purpose flour
  • 8 oz white or cremini mushrooms, thinly sliced
  • 1/2 medium yellow onion, finely minced
  • 2 cloves garlic, minced
  • 1/4 cup dry sherry or white wine (optional)
  • 2 cups whole milk or half-and-half, warmed
  • 1 cup low sodium chicken or vegetable broth
  • 1 tsp fresh thyme leaves
  • 1 tsp Dijon mustard
  • 1 cup Gruyère or Sharp Cheddar cheese, grated
  • Salt and freshly ground black pepper to taste

Instructions:

  1. Prepare the Crispy Shallots: Heat oil in a small saucepan to 325°F (160°C). Fry shallots in batches until deep golden brown and crisp (approx. 3-5 minutes). Remove with a slotted spoon, drain on paper towels, and immediately sprinkle with salt. Set aside.
  2. Prepare the Green Beans: If using fresh beans, blanch in salted boiling water for 3-4 minutes until tender-crisp. Immediately plunge into an ice bath to stop cooking, then drain thoroughly. If using canned beans, rinse very well under cold water and pat dry.
  3. Make the Mushroom Cream Sauce: In a Dutch oven, melt butter over medium heat. Add sliced mushrooms and cook until nicely browned (6-8 minutes). Remove mushrooms and set aside.
  4. Add the minced onion to the pot and sauté until soft (3 minutes). Add garlic and cook for 1 minute until fragrant.
  5. Make the Roux: Sprinkle flour over the onions/garlic mixture. Whisk constantly for 1-2 minutes to cook out the raw flour taste.
  6. Deglaze (Optional): Pour in sherry/wine, scraping up any browned bits, and cook until nearly evaporated.
  7. Build the Sauce: Gradually whisk in the warmed milk until smooth. Then, whisk in the broth, thyme, and Dijon mustard. Bring to a simmer, whisking often, until the sauce thickens enough to coat the back of a spoon (about 5-7 minutes). Season generously with salt and pepper.
  8. Assemble the Casserole: Stir the blanched beans and cooked mushrooms back into the sauce. Fold in half (1/2 cup) of the grated cheese. Pour the mixture into a prepared 9x13 inch baking dish.
  9. Top evenly with the remaining cheese. Bake at 375°F (190°C) for 15-20 minutes, until bubbling and golden.
  10. Remove from the oven. Immediately scatter the reserved crispy shallots over the top. Let rest for 10 minutes before serving.