Dissolve the yeast and sugar in a small bowl of water and let it stand until a frothy layer forms on the top.
Sift together four cups of flour, sugar and a pinch of salt into the bowl of a standing mixer. If you don’t have a mixer, sift the dry ingredients into a dry mixing bowl.
Combine two eggs, one egg yolk and ¼ cup of oil in a small mixing bowl and pour the mixture into the bowl containing the dry ingredients. Whisk the mixture to form a slurry.
Pour the yeast mixture over the slurry and mix with a long handled spoon to form a shaggy dough.
Transfer the dough to a floured working surface, such as your kitchen counter, and knead it well with the palms of your hands for 10 to 12 minutes. If the dough feels very sticky, add more flour spoon by spoon, kneading continuously, until it is soft and smooth, and holds a ball-shape.
Move the dough to an oiled bowl, cover it with plastic wrap, and allow it to rise at room temperature, until it doubles in size (1 ½ to 2 hours).
Divide the dough into three equal parts and roll each part into a long rope, about 16 inches long and one inch thick.
Gather the ropes and join them together at the top. To make a 3 strand challah, braid the ropes together just as you would braid hair, and when complete, squeeze the ends together.
Lightly grease a baking sheet and line it with parchment paper. Transfer the braided dough to the baking sheet, cover it with a clean dishcloth and allow it to rise again, for about an hour.
Brush the challah bread with egg white and bake it in an oven preheated at 350 degrees Fahrenheit for 30 to 35 minutes, or until it is deeply browned.
Remove the challah bread from the oven and allow it to cool on a wire rack, until just barely warm. Slice and serve.