Mix together well the sugar, potatoes, lard, eggs, and salt.
Dissolve the yeast in 1 cup warm water; then add that to the above mixture.
Stir in about 3 cups flour. Add the remaining 2 cups flour while kneading. Knead until the dough is no longer sticky but moist.
Let rise until doubled.
Preheat oven to 325 degrees F.
Roll out dough to a 3/4 to 1-inch thickness. Cut into bun shapes with a jar or doughnut cutter (or cloverleaf or crescent-shaped cutter) and pour on greased cookie sheets about 2 inches apart. Let them rise until puffy but not doubled (they should not be touching).
Brush with milk. Bake until lightly golden brown, about 12 minutes.