In a large mixing bowl, dissolve yeast in warm milk. Add butter, sugar, egg, salt and 2 cups of flour. Stir until smooth. Then stir in enough of the remaining flour to form a soft dough.
Turn the dough onto a floured surface and knead until it is smooth and elastic, about 6-8 minutes. Place the dough in a greased bowl, turning once to grease the top. Cover and let rise in a warm place until doubled in size, about one hour.
Punch dough down. Turn onto a lightly floured surface and divide into thirds. Shape each portion into a rope, about 20 inches long. Braid the three strands then make a wreath by circling the dough and joining the ends together. Cover and let rise until double, about 45 minutes.
Brush with the beaten egg and sprinkle the sesame seeds on top. Bake at 350 degrees for 20-25 minutes or until golden brown. Remove from pan and let cool.