granny's ham and potato gratin for a crowd

How To Make granny's ham and potato gratin for a crowd

• Step 1
  THE POTATOES: Have ready the kettle containing 4 cups of cold water.
• Step 2
  Peel the potatoes and slice them 1/4 inch thick, dropping them into the cold water to cover as you do so. Cover the kettle, and bring to the boil.
• Step 3
  Uncover and boil slowly for 3 to 4 minutes, until barely cooked through and eat several slices to check.
• Step 4
  Drain, cover the kettle again for 3 to 4 minutes to firm up the potato slices, then uncover.
• Step 5
  THE GARLIC AND MUSTARD SAUCE: Make the classic white sauce; cook the butter and flour together in the saucepan until they foam and froth for 2 minutes without coloring.
• Step 6
  Turn off heat and pour in half the hot milk.
• Step 7
  Whisk vigorously to blend as you pour in the rest.
• Step 8
  Simmer for 3 minutes, stirring.
• Step 9
  Remove from heat and whisk in the seasonings.
• Step 10
  Bring to the simmer again.
• Step 11
  Taste carefully, and add additional seasonings to taste.
• Step 12
  ASSEMBLING: Spoon a 1/16-inch layer of sauce on the bottom of the buttered baking dish.
• Step 13
  Set aside 3 cups of the sauce and 1 cup of the cheese for the topping.
• Step 14
  (Swiss or a mixture such as swiss, mozzarella, jack, and/or cheddar.)
• Step 15
  Now, to arrange everything in 4 layers, start with a quart of the potatoes, then a quarter of the ham, follow by a third of the sauce and sprinkle on a third of the cheese.
• Step 16
  Continue in layers, finishing the final layer with the remaining potatoes and ham.
• Step 17
  Spread on the reserved 3 cups of sauce to cover completely, then the last of the cheese.
• Step 18
  AHEAD OF TIME NOTE: May be kept warm uncovered on a hot tray but be sure not to overheat or the potatoes and ham will dry out.
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