Ingredients:

  • 4 cups (600 g) Pre-Cooked Rice (cold)
  • 4 tablespoons (57 g) Unsalted Butter
  • 1/4 cup (30 g) All-Purpose Flour
  • 3 cups (710 ml) Whole Milk (room temperature)
  • 1/2 teaspoon Dry Mustard Powder
  • Pinch Cayenne Pepper (optional)
  • To taste Salt (Kosher or Sea)
  • To taste Freshly Ground Black Pepper
  • 1 1/2 cups (180 g) Mature/Sharp Cheddar, grated
  • 1/2 cup + 2 tablespoons (approx 75 g total) Parmesan Cheese, grated

Instructions:

  1. Prep Ingredients: Grate all the cheeses. Set aside 2 tablespoons of Parmesan for the topping. Ensure your cooked rice is ready and cold.
  2. Preheat Oven: Set oven to 375°F / 190°C. Lightly butter or grease the 9x9 inch baking dish.
  3. Start the Roux: Melt the butter in a heavy-bottomed saucepan over medium heat. Once foaming subsides, sprinkle in the flour.
  4. Cook the Roux: Stir continuously for 60–90 seconds until the mixture forms a paste and smells slightly biscuity, ensuring it does not brown.
  5. Add the Milk (The Béchamel): Slowly whisk in the room-temperature milk, adding only about a third at a time. Whisk vigorously until the mixture is completely smooth after each addition before adding more.
  6. Thicken the Sauce: Bring the sauce to a gentle simmer, stirring frequently. Reduce the heat slightly and cook for 3–5 minutes until it thickly coats the back of a spoon.
  7. Season and Add Cheese: Remove the saucepan from the heat immediately. Stir in the mustard powder, cayenne, salt, and pepper. Add the grated Cheddar and the main portion of Parmesan (reserving the topping).
  8. Melt the Cheese: Stir gently and patiently until the cheese is completely melted and the sauce is uniform and velvety smooth. This results in the Mornay sauce.
  9. Combine Rice and Sauce: Add the pre-cooked rice to the cheese sauce. Fold the mixture gently with a spatula until the rice is evenly coated.
  10. Transfer to Baking Dish: Pour the cheesy rice mixture into the prepared baking dish. Level the top with the back of the spatula.
  11. Finish and Bake: Sprinkle the reserved 2 tablespoons of Parmesan cheese over the top. Bake for 15–20 minutes, or until the sauce is bubbling around the edges and the top is lightly golden brown.
  12. Rest and Serve: Allow the gratin to rest outside the oven for 5 minutes before serving to allow the sauce to set slightly.