Prepare mashed potatoes, according to package directions; cool to room temperature.

In work bowl of mixer, combine potatoes with milk, butter, starter and eggs.

In a separate bowl stir together yeast, 2 cups of flour, sugar and salt; add to starter mixture and beat for 2 minutes at medium speed using dough hook attachment. Add 1 1/2 cups more flour and beat to make a stiff dough. Turn dough out onto a floured surface and knead 8 to 10 minutes; place in a greased bowl, turn to coat, cover loosely and let rise in a warm place until doubled, about 2 hours.

Punch dough down and knead briefly on a floured surface.

Divide into 6 pieces and form each into a strip about 1" thick and 16" long.

Braid 3 strips and form into a loaf, tucking in ends; repeat with remaining 3 strips.

Loaves may be set to rise on a large greased baking sheet (for country style loaves) or in 2 greased 9" x 5" x 3" loaf pans. Cover loaves loosely and let rise in a warm place for 1 to 1 1/2 hours.

Brush tops generously with egg whites and sprinkle with poppy seeds.