Yield: 2 loaves (16 slices each )
Cook potato in boiling water. Drain, reserving 1/2 cup liquid. Mash potato to a make 1/2 cup; reserve.
Using a large bowl with an electric mixer, combine 2 cups of the flour with yeast and sugar.
In a medium saucepan combine milk, reserved 1/2 cup potato water and 2 tablespoons of the butter. Heat over low heat until lukewarm (butter does not need to melt). Pour into bowl containing flour mixture. With electric mixer set at low speed, beat until blended. Beat at high speed for 3 minutes.
With a wooden spoon stir in reserved mashed potato and enough flour, about 2 cups to make a soft dough. Turn out onto a lightly floured board; knead in enough flour, about 1/2 cup, so that dough becomes smooth and elastic, about 5 minutes. Place in a lightly greased bowl; turn dough so that greased side is up. Cover lightly with a towel; let rise in a warm place until double in bulk.
Meanwhile, in a small saucepan melt remaining 4 tablespoons butter. Stir in parsley flakes, onion powder, marjoram, rosemary and black pepper; reserve for use later.
Punch dough down; divide into two equal parts. On a lightly floured board, roll each half into a 12- x 8-inch rectangle. Spread each rectangle with herbed butter mixture. Roll up, jelly roll fashion, from narrow end. Place each roll, seam-side down, in a greased 8 1/2 x 4 1/2 x 2 1/2-inch loaf pan. Cover lightly with a towel; let rise until double in bulk, about 1 hour.
Preheat oven to 400 F. Brush dough with egg; sprinkle with sesame seeds. Bake until golden, about 30 minutes. Remove bread from pans; cool on wire racks.
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