Prepare the crumbs. Combine flour, sugar, and margarine. Mix to form coarse crumbs. Set aside.
Begin by using 4 cups of warm water (3 cups cold water from the sink and 1 cup boiling water). Combine water, yeast, and sugar in the bowl of an electric mixer. Stir and let sit 6-7 minutes.
Add eggs and oil. Add salt and ⅓ of the flour, mix for a few seconds, until combined. Add another ⅓ flour, and mix just until combined, then the last ⅓ of the flour. Add remaining water (or just as much as needed for a nice sticky dough). Mix for 10 minutes on high speed.
Remove dough from mixer and place in a large mixing bowl. Smear the top of the dough with a little oil. Cover and let rise 2 hours.
Right before you are ready to braid the challah, preheat oven to 200ºF. When it reaches that temperature, shut the oven off.
Divide dough into 6 parts. Braid and place in pans. Place braided challah into the warm oven and let rise an additional 1 hour (otherwise you cover and let rise on the counter until it doubles in size, 1 to 1 ½ hours).
Preheat oven to 350ºF.
Brush challah with beaten egg and place crumbs on top. Bake until challah is golden. Challah with crumbs needs to bake a little longer than usual challah.
Recipe by Between Carpools at https://betweencarpools.com/baking-your-rosh-hashanah-challah-these-are-the-best-crumbs-for-your-challah-more-you-need-to-know/