Dissolve yeast in water with one tablespoon sugar and let proof for 10 minutes.

In mixer, place one and a half cups sugar, salt, egg yolks, and egg with 2.2 pounds (one kilogram) flour. Add the yeast mixture. Add another 2.2 pounds (one kilogram) flour with half a cup oil. Mix until thoroughly combined. Add another 2.2 pounds (one kilogram) flour with another half cup oil. Gradually add the final 2.2 pounds (one kilogram) flour with the remaining half cup oil, and dough enhancer, if using. Sometimes you won’t need the entire quantity of flour. (Rule of thumb — less flour is always better. If the dough comes together and is not sticky, don’t use the full amount. Many factors come into play to determine how much flour you’ll need — temperature in the kitchen, power of mixer, quality of flour, etc.)

Put the dough into a greased large bowl or garbage bag and let rise for 40 to 60 minutes. Shape and let rise for another half an hour. Partway through the rising time, preheat the oven to 350 degrees Fahrenheit (175 degrees Celsius).

Brush the challahs with egg wash and sprinkle with sesame and poppy seeds. Alternatively, mix together streusel ingredients to form crumbs. Sprinkle over challahs after brushing with egg wash.

Bake challahs for 30 to 40 minutes, switching the trays halfway through the baking time. Remove from pans to wire rack to cool. Cool completely before freezing.