Soften yeast in warm water.
Combine potato flakes, sugar, shortening, salt and milk in large mixing bowl.
Cool to lukewarm.
Add 1 egg, 1 egg yolk (reserve white) and yeast.
Gradually add flour to form a stiff dough.
Knead on floured surface until smooth and satiny, 5 to 7 minutes.
Place in greased bowl, turning dough to grease all sides.
Cover; let rise in warm place (85° to 90° F.) until light and doubled, 1 to 1 1/2 hours.
Cut each can of SPAM into 6 slices, then cut each slice into 4 strips.
Roll out half of dough on floured surface to 14xl2-inch rectangle.
Cut in half crosswise.
Cut each rectangle into six 7x2-inch rectangles.
Place 2 strips of SPAM down center of each rectangle.
Bring sides to center; seal well.
Place, seam-side down, on greased cookie sheets.
Brush with slightly beaten egg white.
Sprinkle with sesame seed.
Repeat with remaining dough.
Let rise until light and doubled, about 30 minutes.
Bake at 450° for 10 to 12 minutes until golden brown.