Preheat oven to 325°F (DO NOT use convection). In a three-quart saucepan over medium heat, slowly warm
the milk just to a simmer. Add the sugar and whisk constantly until fully dissolved; do not allow the mixture to
boil (lower the temperature if necessary). Once the sugar is incorporated, add the chocolate and peanut butter
and continue to whisk until the liquid comes back to a simmer. Ensure the chocolate has fully dissolved,
but again, do not allow the mixture to boil. Remove from heat and add the vanilla. In a small bowl, whisk the
egg yolks together, then slowly whisk them into the chocolate mixture. Strain the final mixture through a fine
mesh sieve and into a two-quart liquid measuring cup to remove any residual lumps.