Use this chestnut pastry cream to make our Chestnut Cake with Chocolate-Armagnac Glaze.
Fill a large bowl halfway with ice water, and set aside. Whisk together 1/4 cup sugar, the egg yolks, and salt in a bowl. Whisk in cornstarch, 1 tablespoon at a time. Whisk in chestnut puree.
Bring milk and remaining 1/4 cup sugar to a simmer in a saucepan, stirring until sugar has dissolved. Whisking constantly, gradually add half the milk mixture to the yolk mixture. Pour back into pan with remaining milk mixture, and bring to a boil, stirring constantly and scraping bottom of pan. Boil for 2 minutes.
Pour through a fine sieve into a bowl. Place a piece of plastic wrap directly on surface of pastry cream to prevent a skin from forming. Set bowl in ice water, and stir occasionally until cold, about 40 minutes.
Pastry cream can be refrigerated (with plastic wrap directly on surface) for up to 2 days.