In a large bowl, combine 2 cups flour, sugar, yeast and salt. In a saucepan, heat the milk, 6 tablespoons butter, potato flakes and water to 120°-130°. Add to the dry ingredients; beat just until moistened. Beat in egg until smooth. Stir in enough remaining flour to form a stiff dough., Turn onto a floured surface; knead until smooth and elastic, about 6-8 minutes. Place in a greased bowl, turning once to grease top. Cover and let rise in a warm place until doubled, about 1 hour., In a heavy saucepan, combine the egg, cream and salt; cook over low heat until thickened, stirring constantly. Stir in the chives. Cool., Punch dough down. Turn onto lightly floured surface; divide in half. Roll 1 portion into a 16x12-in. rectangle. Spread half of the filling over dough to within 1/2 in. of edges. Roll up jelly-roll style, starting with a short side; pinch seam to seal. Place seam side down on a greased baking sheet; pinch ends together to form a ring., With scissors, cut from the outside edge to two-thirds of the way toward the center of the ring at 1-in. intervals. Separate strips slightly; twist to allow filling to show. Melt the remaining butter; brush over ring. Sprinkle with sesame or poppy seeds. Repeat with remaining dough and filling. Cover and let rise in a warm place until doubled, about 45 minutes., Bake at 350° until lightly browned, 20-25 minutes. Remove from pans to wire racks to cool.