A classic Challah loaf.
Whisk together flour, yeast, and salt in bowl of stand mixer.
In a 4 cup liquid measuring cup or medium bowl, whisk water, oil, eggs, and sugar until sugar has dissolved.
Slowly add liquid ingredients to flour mixture using dough hook on low speed, until cohesive dough starts to form and no dry flour remains, about 2 minutes, scraping bowl as needed.
Increase speed to medium-low and knead dough until dough is smooth and elastic, about 10 minutes. The dough should pull away from sides of bowl but stick to bottom.
Transfer dough to lightly greased large bowl or container, cover tightly with plastic wrap. Let rise until increased in size by about half, 1.5 to 2 hours.
Line 2 baking sheets with aluminum foil and spray with vegetable oil spray. Transfer dough to clean counter and divide into 2 equal pieces. Divide each piece into thirds and cover loosely with greased plastic.
Working with 1 piece of dough at a time, strech and roll into 12-inch ropes (for a total of 6).
Arrange 3 ropes side by side and pinch end together. Braid ropes into loaf and pinch remaining ends together. Repeat with other 3 ropes.
Transfer each loaf to a prepared sheet. Cover loosely with greased plastic and let rise until loaf increases in size by about half, 1 to 1.5 hours.
Make egg wash by beating egg with water and pinch of salt.
Preheat oven to 375 degrees.
Brush loaves with remaining egg mixture and sprinkle with poppy or sesame seeds (if desired).
Bake for 25 minutes until deep golden brown. Transfer to wire rack and let cool completely.
Adapted from Bread Illustrated and Smitten Kitchen.