Au Gratin Potatoes

Ingredients

0 of 10 out on the counter

• 2½ lb Yukon gold potatoes, scrubbed, unpeeled
• ½ yellow onion, finely diced (about ½ cup, 75 g)
• 1 tbsp olive oil
• 5 tbsp all-purpose flour
• 2½ cups skim milk
• ¾ tsp salt
• ½ tsp black pepper
• ⅛ tsp nutmeg
• 6 oz reduced-fat sharp cheddar, shredded from a block (about 1½ cups)
• Oil spray for the dish

All set! Everything is out. Time to bake.

Method

1. 1Heat the oven to 375 °F. Spray a 9×13-inch baking dish.
2. 2Slice the potatoes about ⅛ inch thick, thinner than a pencil, with a food processor or a mandoline. Leave the skins on. Keep the slices in a bowl.
3. 3Warm the olive oil in a large pot over medium heat. Stir in the onion and cook 3 minutes, until soft.
4. 4Whisk in the flour and cook 1 minute. Pour in the skim milk a little at a time, whisking out lumps. Bring to a gentle boil, whisking, and cook about 2 minutes, until it coats the back of a spoon.
5. 5Take the pot off the heat and let it stop bubbling for a minute. Stir in the salt, pepper, nutmeg and two-thirds of the cheese a handful at a time, until smooth. Reduced-fat cheese turns grainy if the sauce is too hot.
6. 6Add the potato slices to the pot and turn them over with a spatula until each slice is coated. Spread them in the dish and press flat. Scatter the rest of the cheese on top.
7. 7Cover tightly with foil and bake 60 minutes. A mile up, water boils at 203 °F, so the potatoes can take up to a quarter longer. Test them with a knife at 60 minutes.
8. 8Take the foil off and bake 20–30 minutes more, until the top is golden, the sauce bubbles at the edges, and a knife slides through the potatoes with no push.
9. 9Rest 15 minutes before cutting so the sauce thickens.
10. 10Refrigerate leftovers within 2 hours. Reheat each portion to 165 °F.