3/4 cup apple cider (you can also substitute all or part orange juice, or water in a pinch)
1 tablespoon active dry yeast
1 large egg
2 large egg yolks
1/3 cup olive oil
1/3 cup honey
1 tsp coarse salt
~4 — 4 1/2 cups flour
3/4 cup chopped chocolate
1 egg, lightly beaten with a splash of water (henceforth known as the egg wash)
flaky salt for sprinkling
Pour the cider in the bowl of a stand mixer, then sprinkle in the yeast. Let sit ~5 minutes, to allow the yeast to soften and bloom.
Add the egg, egg yolks, oil, honey and salt. Fit the mixer with a whisk attachment, and mix until the liquid is well-blended. Add a few cups of the flour, mixing until it forms a batter.
Remove the whisk attachment, and fit the mixer with a dough hook. Add the remaining flour, bit by bit, until a soft and sticky dough is formed that justclears the sides of the mixing bowl, but still sticks to the bottom. Continue kneading with the dough hook for a few more minutes, to form supple, sticky, and well-developed dough.
Lightly oil a large bowl, and turn the dough out into it. Swish it around, then flip it over, so that the top is oiled as well. Cover the bowl, and let rise until doubled, ~1-2 hours, depending upon the temperature of the room. When risen, punch it down to deflate (I like to flip it over at this point, but it's not necessary), and let rise another hour or so (it doesn't need to entirely double this time, but you want to see some rising). The dough can be refrigerated overnight for either of these rises — just remove it and give it an hour to come to room temperature before proceeding with the recipe.
After the dough has risen for the second time, line a baking sheet with parchment or dust it with cornmeal. On a lightly-floured countertop, divide the dough into strands for the braid of your choosing — you can do a standard three-strand braid, or search the internet for an ornate braiding method of your choosing (I'm still obsessed with this foursquare braid, which seems to work particularly well for this challah). After you've divided the dough into portions for your braid, press each portion into a rough oval, and scatter on the chocolate chunks. Roll the dough up into a cylinder, squeezing out any air and sealing the seam. Roll the dough strands out into long ropes (if the dough resists, let it sit for a few minutes to relax). The chocolate chunks may remain inside the dough, or work to the outside — either will make for a good result. Weave the strands into the challah, and place on the prepared sheet.
Brush the dough with the egg wash (a brush is best for this, but I've made do with my fingers at times), and let it rise until it's increased by half, ~45 minutes to 1 1/2 hours, depending upon the room temperature (you want to make sure the final rising is complete — if the challah hasn't risen enough, it can end up either too dense, or expand raggedly in the oven, ruining your pretty shape).
While the dough is rising, preheat the oven to 375° Fahrenheit.
When the dough has completed its final rise, give it another brush with the egg wash (be delicate to avoid deflate all that nice rising that's just happened), and sprinkle generously with the flaky salt. In fact, even more than you think is generous, taking care to sprinkle in the seams and towards the sides, for maximum salty coverage after baking. Transfer to the oven, and bake until the bread is burnished to a dark brown and smells done, ~35-45 minutes (if it's browning too quickly, you can dome with foil for the final 15 minutes of baking, but I tend to favor a dark challah). Transfer to a rack, and allow to cool before slicing. Don't worry — the chocolate will be nice and melty for a few hours.