Ingredients:

  • 3 lbs High-Starch Potatoes (e.g., Russet or Maris Piper), peeled and sliced 2mm thick
  • 1 Tbsp Unsalted Butter (15 g)
  • 1 medium Shallot (50 g), finely minced
  • 3 cloves Garlic, finely minced
  • 3 cups Low-Fat Milk (1% or 2%) (710 ml)
  • 1 cup Low-Sodium Chicken or Vegetable Stock (240 ml)
  • 1 Tbsp All-Purpose Flour (10 g)
  • 5 tsp Fine Sea Salt
  • 1/2 tsp Freshly Ground Black Pepper
  • 1/2 tsp Freshly Grated Nutmeg
  • 2 oz Mature Cheddar Cheese, grated
  • 1 oz Parmesan Cheese, freshly grated
  • 1 tsp Fresh Thyme, chopped (optional garnish)

Instructions:

  1. Preheat oven to 375°F (190°C). Lightly butter a 9x13 inch baking dish.
  2. Peel the potatoes and slice them uniformly thin (1.5mm–2mm). Rinse the sliced potatoes in cold water for 1–2 minutes to remove excess surface starch. Drain well and pat dry with a clean tea towel.
  3. In a heavy-bottomed saucepan, melt the butter over medium heat. Add the minced shallot and sauté until soft and translucent (2-3 minutes). Add the minced garlic and cook for 1 minute until fragrant—do not allow the garlic to brown.
  4. Sprinkle the flour over the shallots and garlic, stirring quickly for 30 seconds to cook out the raw flour taste. Gradually whisk in the low-fat milk and chicken stock until smooth.
  5. Season the sauce with salt, pepper, and nutmeg. Bring the mixture to a gentle simmer, stirring occasionally. Reduce the heat to very low and simmer gently for 5 minutes. Remove from the heat.
  6. Arrange one-third of the potato slices overlapping in the prepared baking dish. Pour one-third of the milk mixture evenly over the potatoes. Sprinkle lightly with a mixture of the Cheddar and Parmesan.
  7. Repeat the layering process two more times, ensuring the final layer of potatoes is completely covered by the remaining sauce. Top generously with the remaining grated cheese mixture.
  8. Cover the dish tightly with foil. Bake for 40 minutes at 375°F (190°C).
  9. Remove the foil. Increase oven temperature to 400°F (200°C). Bake for another 20–30 minutes, until the top is deeply golden brown and the potatoes are fork-tender.
  10. Remove from the oven and let the gratin rest for 15 minutes before serving. This allows the starches to stabilize the sauce, achieving the perfect creamy set.