Why is my pastry cream (custard) grainy?

pasta_paul

I made a simple pastry cream from a recipe that I've used once before uneventfully, and this time it turned out with a grainy texture. The procedure was basically to: whisk together 3 egg yolks and an egg together with sugar and cornstarch in one bowl, separately bring milk with butter to a boil, temper the egg mixture with the hot milk, and then add the warm egg mixture to the milk and boiling for three minutes. What might I have done wrong...

Originally asked by amcnabb on Stack Exchange (cooking) (CC BY-SA 3.0).

uphilltech

Great question — answering as the UphillTech team:

I think it all got too hot, but there might be other problems. Did you mix the cornstarch in completely? Leaving undissolved cornstarch is a sure way to obtain 'blobs'. Did you pour the hot milk onto the egg-mixture? You should do that very slowly and whisk vigorously (while trying to splash everything). If the eggs get too hot, they will coagulate. Did you use a double boiler? Putting the pan on an open flame will make the bottom too hot and the eggs will coagulate. Even if you did use a double boiler, did you whisk regularly while heating? The eggs at the bottom will become far warmer than the eggs in the center... As rumtscho mentioned, a thermometer will be useful for monitoring the...

Full answer by BaffledCook: https://cooking.stackexchange.com/a/25687 (CC BY-SA 3.0).

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