Step 1In a medium saucepan, melt the butter over low heat. Stir in the cardamom, cinnamon, nutmeg and sugar and cook for 1 minute, stirring constantly.
Step 2Stir in the rice, milk and cream. Bring the mixture to a simmer over high heat, then reduce the heat to maintain a simmer. Cook the rice, uncovered, until very tender, stirring occasionally, 20 to 25 minutes.
Step 3Remove from the heat and set the pan aside, uncovered, until the rice cools to room temperature, about 30 minutes to 1 hour. (The pudding will be very soupy at first, but will thicken as the rice continues to absorb the liquid as it cools in the pan.) When the rice is almost cooled, peel and dice the banana.
Step 4Stir in the pistachios and banana, then cover and refrigerate the pudding until well chilled. Garnish with extra pistachios if desired. This makes about 3 cups rice pudding.