Preheat oven to 350° F/ 180°C. Prepare an 8" square pan or 6 small ramekins by spreading the sides with butter.
Cook the rice in 2 cups milk.
(If using cooked rice, reheat, using 1/2 cup of milk to loosen)
Stir in butter and allow to melt.
In a separate bowl beat together the eggs, sugar, salt and the rest of the milk. Add the raisins if using.
Add to the hot rice and butter. Mix well and pour into the pan or ramekins. Sprinkle with cinnamon.
Bake until set (anywhere from 20 to 50 minutes depending on the container).