Emergency Pudding

In a cup, stir together the cornstarch and about ¼ cup of the milk. In a microwave-safe bowl, stir together sugar, salt, egg yolk, and about a tablespoon of the milk until smooth. Slowly whisk in the rest of the milk. Microwave on high for a minute. Whisk in the cornstarch mixture. Microwave another 5 minutes, stopping to stir every minute. Stir in butter and vanilla. Chill.

Note: though the mixture will bubble and thicken early in the process, it’s necessary to boil sufficiently long to deactivate the α-amylase enzyme in the egg yolk, which would otherwise break the tangled starch molecules apart and thin the pudding. Saliva also contains this enzyme, so don’t taste and stir with the same spoon.