Pour yeast, warm water, and sugar into bottom of mixing bowl in stand mixer, fitted with hook attachment. Stir with hook until sugar and yeast are dissolved. If you're worried your yeast might be dead, wait a few minutes for yeast to start foaming. If you're pretty confident your yeast is good to go, proceed to next step.
Add half of the flour and salt, and beat with hook for two minutes.
Add egg, butter and rest of flour. Mix with hook until dough is smooth, and starting to pull away from sides of mixing bowl, about 8 minutes on high speed.
Lightly flour a work surface, and empty dough out of bowl on to surface. Divide dough into three equal portions.
Using flour to assist you, use your hands to roll dough out to 10-12 inch ropes. Once you have three ropes, braid pieces together and tuck in the end.
Line a 12 by 17" sheet pan with parchment, spray parchment, and transfer braided loaf onto sheet pan. Loosely cover loaf with sprayed plastic wrap. Preheat oven to 375 degrees F and allow dough to proof on sheet pan, in a warm spot, for about 1 hour. It'll grow about 50% in size.