Heat oven to 375°F. In small bowl, mix tartar sauce and onion.
Separate dough into 8 triangles. Place 1 fish stick on shortest side of each triangle. Spoon 1 teaspoon tartar sauce mixture onto each fish stick.
Roll up each, starting at shortest side of triangle and rolling to opposite point. (Fish sticks will not be completely covered.) Place roll-ups, point side down, on ungreased cookie sheet. Brush each with butter. Sprinkle with sesame seed.
Bake 11 to 13 minutes or until golden brown.