Of course if it were only cornstarch, milk, and sugar that went into pastry cream, all we’d need to do is put the pot on the stove, turn on the gas and stir. But there is the somewhat (and I mean only somewhat) tricky matter of the eggs, which require that we do some tempering. Tempering is just a fancy word for heating slowly or in stages. We do this so that heat-sensitive ingredients like, say, eggs, don’t get too hot too fast, causing them to clump up and sink to the bottom of the pan. Custards are where the lion’s share of tempering happens in the kithcen, though depending on how much you like working with chocolate you get to do a pretty fair amount of it.
With pastry cream it’s a pretty fool-proof process (though the good news is that if you mess it up you can simply strain the cooked egg out of the milk mixture and try it again). Simply heat your milk to boiling, then pour about a third of it into the mixing bowl where your mixture of egg yolks, sugar and corn starch awaits. You stir it all together, pour the whole mess back in the pan with the rest of the milk and…ba-dum-bum, you’ve just tempered. Not so very hard at all.