From The Bread Book by Lena Sturges.
Dissolve yeast in water. Heat milk until almost simmering. Into large bowl measure sugar, mustard, salt, pepper, 2 Tbsp instant minced onion and shortening. Stir in milk until sugar dissolves and shortening melts. Cool to lukewarm. Stir in about 2 cups flour and beat until smooth. Beat in yeast. Stir in enough additional flour to make a moderately stiff dough.
Onto lightly floured surface, turn out dough and kenad until smooth and satiny, 5 to 8 minutes. Shape into ball and place in lightly greased bowl, turning to grease all sides. Cover and let rise in warm place until doubled, about 1 1/2 hours. Punch down. Divide dough into 2 equal portions; shape into balls. Let rest 10 minutes. Meanwhile, grease two large baking sheets.
Roll or pat each half of dough into a 9-inch square. Using sharp knife, cut each into 9 squares. Tuck corners under to form buns. Place on baking sheet and flatten with palm of hand. Let rise in warm place until doubled, about 30 minutes. Combine 2 Tbsp instant minced onion and 1/4 cup water; allow to stand 5 minutes. Just before baking, sprinkle buns with onion and poppy seeds, 25 to 30 minutes or until golden brown. Yield: 18 sandwich buns.