Heat 3.5 cups milk to very hot, just under boil (microwave 7 minutes)
Put into a small bowl:
1/8 cup sugar
2 heaping Tbsp flour
Stir in enough milk to make a runny paste
Whisk into hot milk slowly.
Put back in the microwave for a minute at a time, stirring in between, until it boils.
Cool for a bit, then add your favorite fruit.