In large mixing bowl, beat butter until light and fluffy. Add the sugar and beat for 10 minutes on medium speed. Add four of the eggs, one at a time, and beat well after each addition. Beat in the vanilla. Combine the flour, baking powder, and salt in a separate bowl. Add to the butter mixture and stir to form soft, cohesive dough. Add flour if dough is too soft to handle easily.
Preheat oven to 350 degrees F. Grease cookie sheets
Lightly flour a work surface. Break off 1 inch lumps of dough and roll on floured surface into ropes about 7 inches long and 1/4 inch in diameter. Cross the ends and twirl dough in a loop in the opposite direction, forming a braid. Place on cookie sheets about 1 inch apart.
Beat remaining egg. Brush onto braids for glaze and sprinkle with sesame seeds. Bake 20 to 25 minutes. Let cool on cookie sheets for 10 minutes, then remove to racks to cool completely.