Heat the heavy cream and whole milk in a saucepan until steaming. Keep it at a gentle simmer, with small bubbles around the edges, not a rolling boil.

In a bowl, whisk the egg yolks and granulated sugar until smooth, then slowly whisk the steaming dairy into the yolks. Pour in a thin stream while whisking to avoid scrambling.

Return the mixture to the saucepan and cook over medium-low heat, stirring constantly, until the custard reaches 175°F. The custard should coat the back of a spoon and look slightly thicker with a steady temperature climb.

Remove the custard from heat and whisk in the creamy peanut butter until completely smooth. Scrape the bottom and corners so no streaks remain.

Strain the custard through a fine mesh sieve, then whisk in the vanilla extract and salt. Discard any solids and keep whisking until the mixture looks uniform.

Cool the custard in an ice bath, stirring occasionally until it feels much colder. The surface should stop steaming and the bowl should cool down quickly against the ice.

Refrigerate at least 4 hours or overnight until thoroughly chilled. Cover it so a skin doesn’t form and the texture stays smooth.

Churn the chilled custard in an ice cream maker according to the manufacturer’s instructions. Stop when it reaches a thick, soft-serve consistency.

Transfer to a freezer-safe container and freeze until firm. The ice cream should scoop cleanly after it hardens.