Pour water (should be generally between 105°F and 110°F) into mixing bowl of electric mixer. Sprinkle with yeast and about 1 teaspoon of the sugar. Stir gently to hydrate the yeast. Let it sit for 5-10 minutes to get foamy. (If using instant yeast, skip to the next step and add yeast with the flour and other ingredients.)
Add the flour, rest of the sugar, yolks, oil, and honey. With the dough hook attachment, knead the mixture for about 3-5 minutes.
With the mixer on low, slowly add the salt. Knead for an additional 2-3 minutes until the salt is fully absorbed and the dough passes the windowpane test. (If making an entire batch with raisins, once the dough passes the windowpane test, add 219 grams (1½ cups) raisins and knead until fully incorporated. If using part of the dough for raisins, knead the raisins into the portion of dough as described in step 6.)
Place dough in ungreased bowl, cover with plastic wrap, and let rise in warm area for about 3 hours.
Gently deflate the dough by pulling a piece from the bottom and folding it over itself, turning the bowl so you can do four similar folds.
Weigh the dough and divide into two or three equal portions, depending on how many challahs you are making. If dividing into two and you want to make one of them with raisins, knead in 110 grams (¾ cup) of raisins. If dividing into three and you want to make one of them with raisins, knead in 73 grams (½ cup) raisins.
Further divide each portion into the number of strands you be making for each braid. Tip: If you plan to make a traditional 3 strand braid, you can divide the total amount of dough into either two or three portions for two or three challahs. If you plan on making a four, five or six braided challah, I recommend dividing the total dough into two portions.)
Shape each portion into a ball, covering with plastic wrap as you continue to shape the portions of dough.
Press down each ball into an oval. Fold the top third of the oval over itself towards you. Fold the top part again over the rest of the dough. Using the palms of both hands, roll the dough against the countertop to create your strands. If the dough starts pulling back, cover it with plastic wrap and allow it to rest for 10 minutes. Braid and shape as desired.
Cover loosely with plastic wrap and let rise 1 to 1½ hours.
Towards the end of the rising time, preheat oven to 350° F.
Apply egg wash. Sprinkle challah with any toppings, if using. Bake 25-35 minutes until golden brown on top and sides. The internal temperature should be over 190℉.