In a microwave-safe bowl, combine the egg yolk, soy milk, and sugar, and whisk very well.
Next, add the rice flour and mix thoroughly.
Cover the bowl with plastic wrap, and microwave for 2 minutes. Take out of the microwave and mix quickly.
Again, cover the bowl with plastic wrap, microwave for another minute, take it out, and mix quickly. If it has reached the desired consistency, it's done if not, microwave for a bit longer in 30 second increments.
Story Behind this Recipe
I wanted to come up with a custard cream recipe that didn't need to use wheat flour.