Dissolve 1 teaspoon sugar in ½ cup water in the bowl of a stand mixer.
Sprinkle yeast over water and mix, let stand 10 minutes until foamy.
Add the next 6 ingredients to mixing bowl and mix with dough hook for 6 minutes.
Dough should be a little sticky. Place in oiled bowl, cover and let rise in warm place until doubled in bulk (1 hour). Punch down dough. Let rise until doubled in bulk again (1 hour)
Punch down again. Divide dough into 3 equal parts. Roll dough into three long strands and lay strands out on a cookie sheet. Braid them, tucking ends under. Cover with a towel and let rise for another 40 minutes or until doubled,
Brush with beaten egg yolk, sprinkle with seeds if desired, then bake in a preheated 375 degree oven for approximately 35 minutes or until golden brown. Check after 20 minutes, and if the Challah is a deep golden brown after 20 minutes, then shield it loosely with foil.
The challah is done when it sounds hollow when thumped on the bottom.