- 2 cups whole milk
- 1 cup heavy whipping cream
- 1/2 cup white sugar
- 1/2 cup unsweetened cocoa powder
- 4 egg yolks
- 3/4 cup semisweet chocolate chips
- 1/2 teaspoon vanilla extract
- 3/4 cup peanut butter, or to taste
- Stir whole milk, heavy cream, sugar, and cocoa powder together in a saucepan over low heat; cook, stirring, until sugar and cocoa powder have dissolved, about 5 minutes.
- Beat egg yolks in a bowl with an electric mixer until thick and pale yellow, about 4 minutes. Stir about 1/2 cup of cocoa mixture into egg yolks, whisking constantly.
- Pour egg yolk mixture into cocoa mixture; cook, stirring constantly, until the mixture is thick enough to coat the back of a wooden spoon, about 5 minutes. Pour cocoa mixture into a bowl.
- Place chocolate chips in a large microwave-safe bowl; heat in microwave in 20 second intervals until warm, stirring until chocolate chips are melted. Stir chocolate chips and vanilla extract into cocoa mixture just until combined; refrigerate until cold, about 2 hours.
- Freeze chocolate mixture in ice cream maker according to manufacturer's instructions. Drop peanut butter by spoonfuls into ice cream; using a knife, fold peanut butter through ice cream to form ribbons of peanut butter throughout.