In large bowl of electric mixer, thoroughly mix undissolved yeast with 1/3 of the flour and all other dry ingredients. In a 2 to 4 cup measure, start with 1 1/4 cups cold water. Add margarine, then add enough water to make 2 cups liquid. Heat liquids with margarine over low heat until very warm, 110 to 120 degrees. Margarine does not need to melt. Add liquids to dry ingredients. Beat for 2 minutes at medium speed of electric mixer, scraping bowl occasionally. Add about 1/2 cup flour, or enough flour to make a thick batter. Add the 3 eggs one at a time. Beat on high speed for 2 minutes, scraping bowl occasionally. Use dough hook or wooden spoon to stir, adding all but one cup of flour or as much as is needed to make elastic dough. Amount will vary according to temperature and humidity of room. If raisins are used, add here and stir thoroughly. Turn dough out on floured surface, kneading until it becomes smooth and satiny to the touch. Add more flour if needed. Place dough in well-greased bowl, turning to grease top of dough. Cover with plastic wrap and let rise until doubled in bulk, about 1 to 1 1/2 hours. Punch down. Return to lightly floured board. Cut into desired amount of loaves. This recipe makes 1 very large, 2 large or 3 medium loaves. Cut amount of dough desired. Stretch into one strand and twist to form a crown.
Paint egg mixture. Repeat with remaining dough. Tops may be sprinkled with sesame or poppy seeds. After bread has risen for about an hour, brush any dry areas with egg wash. Prick any air bubbles. Bake in 375-degree oven for 25 to 30 minutes, until browned. A flick of finger should produce a hollow sound. Remove to rack to cool. Challah freezes well but should be thoroughly cooled before wrapping in heavy foil.