Chill the ice cream bowl for at least 24 hours or until solid. You should not hear any water sloshing around when you shake the bowl. Mix together 1 cup of the peanut butter and powdered sugar in a bowl until smooth. Line a baking sheet with parchment paper or wax paper. Spoon the peanut butter mixture onto the parchment paper. Spread with a spatula until you get a thin layer, about ½ inch high. Freeze until firm or ready to use. Cut into small cubes before using. 

In a medium bowl, whisk together the egg yolks and granulated sugar until smooth and pale yellow in color.

Add the milk, cocoa powder, and salt to a saucepan over medium heat. Whisk together until combined. Bring the milk mixture to a simmer and then remove from the heat. Be sure not to boil. 

Add about 1/2 cup of the hot milk mixture to the egg and sugar mixture and whisk constantly until combined. Then, add the tempered egg mixture back into the saucepan with the remaining hot milk.

Heat the saucepan on low. Stirring constantly, heat until the base has thickened enough to coat the back of a spoon. This should take a few minutes. Strain the mixture into a bowl to remove any pieces of egg that may have cooked. 

Add the chopped chocolate and the remaining ½ cup of peanut butter. Stir until they have melted completely into the custard. Add the heavy cream and vanilla extract and stir to combine. Cover the bowl with plastic wrap making sure to have the plastic wrap touching the surface of the ice cream base. This will help keep it from forming a skin while chilling. Refrigerate for at least 3 hours, or until cold. 

Churn the ice cream mixture in the bowl of your ice cream machine according to your manufacturer’s instructions (mine took about 20 minutes), until it is thick and the consistency of soft-serve ice cream.  In the last two minutes of the churn, add the frozen peanut butter nuggets. 

Spoon the ice cream into a shallow container or a loaf pan. Press plastic wrap or wax paper to the surface of the ice cream. Freeze for at least 4 hours, or until solid. Let sit at room temperature for about 5 minutes before serving.