Heat butter in a large skillet over medium heat. Fry the cashews and raisins until golden brown. Remove from pan, and set aside. In the same pan, fry the dry pasta pieces until golden brown, about 5 minutes.
Add the milk to the skillet, and increase the heat to medium. Bring to a boil, then reduce the heat back to low; simmer until the spaghetti is tender, and the milk is thickened. Stir in the sugar, cashews and raisins; turn off heat, and let stand for 30 minutes. Serve hot or cold.