Ingredients:

  • 1.35 kg Russet or Yukon Gold potatoes, peeled
  • 1 large yellow onion, sliced into paper-thin half-moons
  • 85 g unsalted butter
  • 30 g all-purpose flour
  • 475 ml whole milk
  • 235 ml heavy cream
  • 3 cloves garlic, smashed
  • 1 tsp fresh thyme leaves
  • 0.5 tsp ground nutmeg
  • 1.5 tsp sea salt
  • 0.5 tsp freshly cracked black pepper
  • 170 g Sharp White Cheddar or Gruyère, shredded
  • 1 tbsp fresh chives, minced

Instructions:

  1. Preheat your oven to 180°C.
  2. Peel your 1.35 kg of potatoes and slice them into 3 mm rounds. Keep them in a bowl of cold water if you aren't using them immediately to prevent browning. Note: Pat them very dry before layering to avoid watering down the sauce.
  3. Melt 85 g of butter in your saucepan over medium heat. Whisk in 30 g of flour and cook for 2 minutes until it smells slightly nutty and toasted.
  4. Slowly pour in 475 ml of whole milk and 235 ml of heavy cream, whisking constantly. Add the smashed garlic, thyme, nutmeg, salt, and pepper. Simmer for 5 minutes until the sauce coats the back of a spoon.
  5. Grease your baking dish. Arrange a third of the potatoes in an overlapping pattern, then top with a third of the sliced onions and a splash of the cream sauce. Repeat these layers. Note: This ensures every potato is kissed by the sauce.
  6. Cover the dish tightly with foil. Bake at 180°C for 45 minutes until the potatoes are tender when pierced.
  7. Remove the foil and sprinkle the 170 g of shredded cheddar evenly over the top. This is where the magic happens.
  8. Return the dish to the oven, uncovered, for another 20 to 30 minutes. Watch closely until the top is golden brown and the edges are violently bubbling.
  9. Remove from the oven and let it sit for 15 minutes. Note: This allows the starch to set so the sauce doesn't run everywhere when sliced.
  10. Garnish with the minced chives right before serving to provide a fresh contrast to the rich, heavy cream.