Ham and Yukon Gold Potato Cakes

    6 tablespoons (about) butter
    3 cups finely chopped leeks (white and pale green parts only;
      from 3 large leeks)
    1/2 teaspoon dried thyme
    1 1/2 teaspoons sugar
    1 1/4 pounds Yukon Gold potatoes, peeled, coarsely grated,
      squeezed dry in kitchen towel
    4 ounces thinly sliced ham, cut into 1x1/4-inch strips
    1/4 cup all purpose flour
    1 large egg, beaten to blend
    1 teaspoon salt
    1/2 teaspoon ground black pepper

Melt 2 tablespoons butter in large nonstick skillet over medium
heat. Add leeks and thyme; saute until leeks begin to soften, about
4 minutes. Cover; reduce heat to low. Cook until leeks are tender,
stirring often, about 8 minutes. Add sugar; saute uncovered until
leeks are very soft, about 4 minutes. Transfer to medium bowl; cool.

Preheat oven to 250F. Place large rimmed baking sheet in oven. Mix
potatoes, ham, flour, egg, salt, and pepper into leek mixture in
medium bowl. Melt 2 tablespoons butter in large nonstick skillet over
medium heat. Working in batches, add potato mixture by 1/4 cupfuls to
skillet; flatten each to 3- to 3 1/2-inch round. Saute until brown
and cooked through, about 4 minutes per side. Transfer potato cakes
to baking sheet and keep warm in oven while preparing remaining
potato cakes. Add more butter to skillet as needed for each batch.