Heat oven to 300 deg F
9in ovenproof dish 3in deep (2 qt), lightly buttered.
Mix the evaporated milk, whole milk and cream together, then place the rice and sugar in the ovenproof dish, pour in the liquid and give it all a good stir. Grate the nutmeg all over the surface.
Put in center of oven for 30 mins. Give a good stir then in the oven again for 30mins.
Dot the butter all over and give a good stir then cook for further 50mins (without stirring).
What you are aiming for is for the rice grains to become swollen, with pools of liquid all around them, and the whole thing covered with a brown skin. If the mixture is still too wet and the top not brown enough, add more time. What you don't want is the mixture too dry and the rice grains stuck together.