Line one 8-by-12-inch glass or metal baking pan and one 8-by-8-inch glass or metal baking pan with parchment paper.
Fill a large bowl with ice and water; set aside. Combine egg yolks and sugar in the bowl of an electric mixer fitted with a whisk attachment. Beat at medium-high speed until very thick and pale yellow, 3 to 5 minutes. (Alternatively, whisk egg yolks and sugar together in a medium bowl.)
In a medium saucepan, bring milk just to a simmer. With mixer running on low, use a measuring cup or ladle to slowly pour about 1/2 cup of the hot milk into the egg-yolk mixture, beating constantly until blended. Continue, adding about 1/2 cup milk at a time, until all has been added.
Return mixture to saucepan; cook over medium-low heat, stirring constantly with a wooden spoon, until mixture is thick enough to coat back of spoon, 3 to 5 minutes. The custard should retain a line drawn across back of spoon with your finger. Whisk in 1 cup peanut butter.
Remove pan from heat, and stir in cold heavy cream. Pour custard through a mesh strainer into a medium bowl set in the ice bath; stir occasionally until cool. Stir vanilla into cooled custard. Cover bowl and refrigerate at least 30 minutes or overnight.
Pour the custard into a chilled ice-cream maker; freeze according to manufacturer's instructions. (The ice-cream mixture will be set but not hard.)
Swirl in remaining cup of peanut butter; transfer two-thirds of the soft ice cream, or 1 quart, to larger baking pan, smoothing the surface with an offset spatula. Transfer remaining third (1/2 quart) to smaller pan, smoothing its surface. Cover each pan with plastic wrap; freeze overnight. Ice cream may be made to this point up to one week ahead.
Save to your Collections
Sorry for the inconvenience! Saving is temporarily unavailable as we work through a few kinks in our new recipe design (we hope you like it!). Don't worry, your collections are safe and you'll be able to save recipes again very soon.
Review this Recipe
Reviewing recipes is temporarily unavailable as we work through a few kinks in our new recipe design. You'll be able to comment again soon. Sorry for the inconvenience!