In large bowl of an electric mixer, beat butter and sugar until creamy. Beat in 2 of the egg yolks, one at a time. Mix in 3 tablespoons of the half and half.
In another bowl, stir together flour, baking powder, and salt; gradually add to butter mix and blend.
To shape cookies, pinch of 1 inch balls of dough and roll each into a 7 inch strand. Bring ends together and twist, to form a twirled look to each one.
Beat remaining egg yolk with remaining half and half and brush lightly over cookies and sprinkle with sesame seeds. Bake for about 15 minutes or until golden.
