In a medium bowl, whisk together the egg and sugar until light and fluffy.
Whisk in the milk, vanilla extract, cinnamon, and salt.
Add the cooked rice, and stir until well-combined.
Divide the mixture between two tall mugs.
Microwave on full power for 2 to 4 minutes, until the pudding has set. (Cooking time will vary greatly depending on your microwave and the width and depth of the mug.
Start with 2 minutes and continue cooking in 30-second increments until it is done.) •
Carefully remove the mugs from the microwave and let them stand for a minute or two before serving.
Notes
If you like, top each pudding with an extra sprinkle of cinnamon, citrus zest, raisins, or whipped cream.