In a medium saucepan, add in the heavy cream, milk, 1and ½ cups peanut butter, brown and granulated sugar. Heat on medium heat until the sugar is dissolved and the peanut butter has melted into the cream. Whisking the mixture will help incorporate the peanut butter. It took 18 minutes for mine to come together completely.
Once the peanut butter is melted into the mixture, remove from the heat and add the vanilla extract. Stir to combine.
Place the peanut butter ice cream base into a bowl and cover with plastic wrap. Place into the fridge to chill overnight.
Pour into the ice cream maker for the recommended time required by your ice cream maker. Mine recommends no longer than 20 minutes.
In a loaf pan, add a third of the ice cream. Layer a third of the hot fudge sauce, remaining peanut butter, and chopped Reese's Pieces. I heated my peanut butter for 20 seconds so it's just slightly runny.
Add another third of ice cream, hot fudge sauce, peanut butter and chopped Reese's Pieces. Repeat the layering one more time. Use a skewer and swirl the ice cream.
Cover with plastic wrap and place into the freezer to freeze for 2 hours or until firm.