NOTE: This isn't an old family recipe. I found it on the web. But it worked for even a shlemiel of a baker like me, so it must be good. Makes 2 large loaves.
1 1/2 packages active dry yeast (1 1/2 tblsp.)
1 tblsp plus 1/2 c. sugar
1/2 c. olive or vegetable oil, plus more for greasing the bowl
5 large eggs
1 tblsp. salt
8 to 8 1/2 c. all-purpose flour
1/2 c. raisins per challah (optional), plumped in hot water and drained
Poppy or sesame seeds for sprinkling (optional)
In a large bowl, dissolve yeast and 1 tablespoon sugar in 1 3/4 cups of lukewarm water.
Whisk the oil into the yeast, then beat in 4 eggs, one at a time, with remaining sugar and salt. Gradually add flour. When dough holds together, it is ready for kneading.
Turn dough onto a floured surface and knead until smooth. Clean out bowl, grease it, then return dough to bowl. Cover with a cloth or plastic wrap, and let rise in a warm place for 1 hour, until almost doubled in size. Dough may also rise in an oven that has been warmed to 150 degrees then turned off. Punch down dough, cover and let rise again in a warm place for another half-hour.
After the second rising, knead the raisins if you're using them. Then form the bread into loaveseither in a loaf pan, braided into a long loaf (3-strand or 6-strand braids about a foot long), or circular (create 3 strands, about a foot long, then join their ends and form them into a spiral). Put them on a greased cookie sheet with at least two inches between them.
When the loaves are formed, beat the remaining egg and brush half of it on the loaves. Let it rise another hour. Then preheat the oven to 375º and brush the loaves with the rest of the egg. Sprinkle on the seeds if you're using them.
Bake in middle of oven for 30 to 40 minutes, or until golden and sounds hollow when tapped on the bottom. Cool loaves on a rack.
Source: Adapted from Joan Nathan, found on smittenkitchen.com