Bring 1 quart water to a boil; add chopped sweet potato, and cook 10 to 15 minutes or until tender. Drain, reserving 1 cup liquid; cool liquid to 110°.
Mash potato; stir in 2 tablespoons sugar. Set aside.
Stir remaining 1 tablespoon sugar and yeast into reserved liquid; let stand 10 minutes.
Combine 5 1/2 cups flour and salt in a large bowl; make a well in center of mixture.
Combine mashed potato mixture, milk, eggs, and oil; add yeast mixture, stirring until blended.
Add to flour mixture, stirring until a soft dough forms.
Turn dough out onto a floured surface, and knead lightly, adding 1/2 cup flour, as needed, to prevent sticking. Place in a well-greased bowl, turning to grease top. Cover and let rise in a warm place (85°), free from drafts, 1 hour or until doubled in bulk.
Punch dough down; turn out onto a floured surface, and divide in half. Shape each portion into an 18- x 2 1/2-inch log.
Cut each log diagonally into 1-inch-thick slices; sprinkle tops of slices with remaining 1/4 cup flour, and place 1 to 2 inches apart on lightly greased baking sheets. Cover and let rise in a warm place, free from drafts, 20 minutes.
Bake at 400° for 15 to 20 minutes until golden brown. Transfer to wire racks to cool.