Beat butter at medium speed with an electric mixer until fluffy. Add cheese and sour cream, beating until blended.
Combine flour and Italian seasoning. Gradually add to butter mixture; beat at low speed until blended. Cover and chill 30 minutes.
Turn dough out onto a lightly floured surface; knead 3 or 4 times. Divide dough in half. Roll half of dough into a 12- x 6-inch rectangle. Cut into 6- x 1/2-inch strips. Stir together egg yolk and 1 tablespoon water; brush over breadsticks. Sprinkle with 1 tablespoon sesame seeds. Twist strips, and place on lightly greased baking sheets. Repeat with remaining dough, egg wash, and sesame seeds.
Bake at 350° for 15 minutes or until golden. Freeze up to 3 months, if desired.