Place the yeast into a bowl suitable for mixing the dough.
Place the egg, whole, into a graduated measuring cup and cover with sufficient water to bring the level to 3/4 cup.
Pour the water into bowl and leave to sit in a warm place until the yeast begins to foam slightly.
Meanwhile, mix the dry ingredients together in such a fashion that the sugar and salt are well distributed; sift if necessary.
Warm the butter so as to make it easy to work into the dough. Alternatively, liquify it, but without making it hot.
Once the yeast is ready, add the mixed dry ingredients, and mix together as well as possible. There isn’t sufficient liquid at this point to make anything resembling a final dough, but the yeast will be incorporated into the dry ingredients before the next step.
Next, incorporate the egg, and finally, the butter.
Once reasonably mixed, dump the dough onto a suitable surface and knead well.
Form the dough into a ball, cover with a bit of vegetable oil—just enough to keep it from drying out, no more—and return it to the bowl.
Cover the bowl with plastic wrap to keep out draught and foreign matter, and place it in a warm place to rise—this is likely to take forty (40) minutes or so, and perhaps longer.
Once the dough has roughly doubled in size, return it to the work area. Punch it down, then break it into two pieces, one being twice the size of the other.
Roll out the smaller piece into a longish sausage shape, similar in proportions to a standard wiener or frankfurter. Do the same with the larger piece, maintaining the diameter but doubling the length.
Braid the two pieces together. This is most easily done by laying out the longer piece in a V shape and placing the shorter piece between the branches of the V with one end over its tip, and then alternately folding the right length over the middle one, followed by the left, and so on. Do this about four times per side, as the thickness and length of the dough allows.
Cover loosely and allow to rise once again, until roughly doubled in size.
Brush the top of the braid with the egg yolk (or other glaze) if desired. At your option, sprinkle with topping.
Bake in an oven preheated to 375°F/190°C for 20–25 minutes. Monitor the baking to ensure the degree of browning desired.