Make the ice cream: In a 1-quart container with a lid, stir together the heavy cream, milk, and 1 1⁄2 cups of the peanuts. Tuck this in the refrigerator overnight. Roughly chop the remaining peanuts and set aside.
The next day, whisk together the egg yolks, sugar, vanilla extract, and salt in a medium bowl. In a 2-quart saucepan, heat the cream and peanut mixture to just under a boil. Slowly whisk half of this mixture into the yolks, taking care not to scramble the eggs. Transfer the tempered yolks to the saucepan, and stirring the whole time, cook until the mixture coats the back of a spoon, 10–12 minutes.
Strain it all through a fine-mesh sieve and discard the tired peanuts. Chill the ice cream base thoroughly—ideally overnight. Process the ice cream according to the manufacturer's instructions for your frozen dessert machine. During the last few minutes of freezing, pour in the chopped peanuts. Let this ice cream spend at least 3 hours in your freezer before serving.
To serve, chill 4 glasses. Drop a nice scoop of peanut ice cream in the bottom of each glass, top with roughly 1⁄2 cup Pepsi, and finish with bourbon to your liking.