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1
Rub a 9- by 12-inch gratin dish with: Butter.
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2
Peel and slice about 1/16 inch thick: 4 large yellow potatoes (about 1 1/2 pounds).
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3
Make a layer of potato slices in the gratin dish, overlapping them slightly, like shingles.
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4
Sprinkle with: Salt and fresh-ground black pepper.
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5
Continue to layer the potato slices, seasoning each layer, until the potatoes are used up.
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6
You should have two or, at the most, three layers.
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7
Carefully pour over the potatoes: 1 cup milk.
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8
The liquid should come up to the bottom of the top layer of potatoes.
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9
Add more if necessary.
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10
Generously dot the top of the potatoes with: 3 tablespoons butter, cut into pieces.
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11
Bake in a 350F oven until browned and bubbling, about 1 hour.
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12
Halfway through the baking, take the gratin dish out of the oven and press the potatoes flat with a metal spatula to keep the top moist.
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13
Return to the oven and keep checking.
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14
The gratin is done when the potatoes are soft and the top is golden brown.
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15
Peel and smash a garlic clove and rub it all over the inside of the gratin dish before buttering it.
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16
Use duck fat instead of butter.
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17
Use heavy cream or a mixture of half-and-half and cream.
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18
Omit the butter.
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19
Substitute celery root, parsnip, or turnip slices for up to half the potatoes.
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20
Add chopped herbs such as thyme, parsley, chives, or chervil between the layers.
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21
Saute mushrooms, sorrel, spinach, or leeks, and layer them between the potato slices.
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22
Sprinkle grated Gruyere or Parmesan cheese on each layer and sprinkle more on top for the last 15 minutes of baking.
