Koulourakia (Greek Butter Twist)

3/4 cup butter, softened
1/4 cup shortening
1 cup granulatedsugar
3 eggs
1 teaspoon vanilla extract
4 cups all-purpose flour
1 tablespoon baking powder
1/4 teaspoon baking soda
1 egg yolk, beaten
1 tablespoon water
2 to 3 teaspoons ground cinnamon
2 to 3 teaspoons sesame seeds

Cream butter and shortening in a large mixing bowl; gradually add sugar, beating well at mediumspeed of electric mixer. Add eggs, one at a time, beating well after each addition. Add vanilla extract;beat until blended. Combine flour, baking powder and baking soda; gradually add to creamedmixture, mixing after each addition. Chill dough 1 to 2 hours.
Divide dough into fourths. Divide each fourth into 16 portions. Roll each portion into a 4-inch rope;fold each rope in half, and twist. Place twists 2 inches apart on greased baking sheets. Combine eggyolk and water; brush over twists. Sprinkle lightly with cinnamon and sesame seeds. Bake at 325degrees F for 20 to 25 minutes or until light golden brown. Immediately transfer to wire racks to cool.