based on the La Brea sourdough book
morning 1, make the sponge:
1.5 c boiling water
1 4-oz-single-serving-cup applesauce (very handy for baking since I never get through a whole jar)
1.5 c white bread flour
1/2 c whole wheat flour
1/2 c starter
Pour boiling water over saffron and let cool until it will warm up the starter but not kill it. Stir together all ingredients in a large bowl, cover with plastic wrap, and leave on the counter until evening.
evening 1, make the dough:
3 whole eggs + 2 yolks, stirred together a little bit
1 packet active dry yeast
3 T canola oil
1 T barley malt syrup
1/4 c sugar
1 T salt
4-6 c white bread flour (book says 2 c bread flour + 1 c semolina + 1 c durum)
Add everything except the flour to the sponge and stir to combine. Add 3-4 c flour a cup or two at a time, stirring and/or kneading in the bowl until the dough is heavy and coherent. Turn onto a floured surface and knead for several minutes, incorporating quarter or half cups of flour judiciously, until the dough is pliable and smooth (but stodgier and less tight than a good just-white-bread dough), and still slightly sticky. Spray-grease the largest bowl that will fit in your fridge and put the ball of dough in it, turning the dough to coat all sides. Cover tightly with plastic wrap, let sit on the counter to get some extra warm-time if your house is on the cool side, then put in the fridge overnight.
morning 2, shape and bake:
2 parchment-lined, semolina-dusted baking sheets
2 egg yolks + <1 T water, stirred together
Remove the dough from the fridge as soon as you can drag yourself out of bed; the dough should have about doubled in size. Dump the dough onto a floured surface, cover with a cloth, and go back to bed until the dough warms up to closer to room temperature. Cut the dough into three equal-sized pieces for each loaf you want to make. You probably want two big loaves, so cut the dough into six equal pieces. I made one huge round double-decker loaf, i.e. half the dough on the bottom (3 pieces each 1/6 of the dough) and a quarter of the dough on top (3 pieces each 1/12 of the dough), and two small loaves with the rest (2 x 3 pieces each 1/24 of the dough). Cover the pieces of dough with the cloth, and let rest until they've warmed up a bit more and are nice and stretchy.
Roll each piece into a good-sized rope--it needs to be rather long and thin for round braided loaves, but shorter and fatter for normal braided loaves. Line up three matching pieces of dough parallel and close to one another. Starting in the middle and working toward each end, braid the three strands together. For straight loaves, braid up to the ends, and smush the ends together into a rounded tip. For round loaves, leave little tails at each end, curve one end to the other to form a loop, and smush each tail on one end into a matching tail on the other end; if the side you're looking at after this smushing looks a bit odd, flip it over and the other side may magically be more aesthetically pleasing.
Place each loaf onto a semolina-ed spot on a baking sheet, making sure to leave plenty of room between loaves. If you're making a double-decker loaf, put the smaller top-layer braid on top of the larger bottom-layer braid now. Cover with a cloth again and let rise. Now is a good time to start preheating the oven to 450F, and for extra warmth you can put the baking sheets on top of the stove, or on top of large level pots on top of the stove if your stove gets extra-hot spots when the oven is on.
When the bread is about doubled and the oven is toasty, brush the top and sides of each loaf with the egg wash. Put the baking sheets in the oven (on racks in the middle but with enough room between for rising), turn the oven down to 400F, and spritz the sides of the oven with water if you have a spritz bottle handy. After 15 minutes, check for uneven browning and rotate the baking sheets. Bake for 10-20 more minutes, shorter for smaller loaves and longer for larger loaves, until evenly browned on the sides, top, and bottom, and hollow-sounding when tapped on the bottom.
Cool on a cooling rack for a bit, but start eating pretty much as soon as you want. If you've reserved the egg whites and have some egg yolk left over, make shakshuka and eat some challah with it. If it's Rosh Hashanah, eat a round loaf with apples and honey and friends.