Line a cookie sheet with a silicone baking mat or parchment paper.
Melt 1 1/2 cups of chocolate chips and 1 teaspoon of shortening in a microwave-safe bowl. Heat in 30-second intervals , stirring in between, until the chocolate is fully melted and smooth.
Dip each graham cracker half into the chocolate, gently tapping it to shake off the excess chocolate, until fully coated.
Place the chocolate covered graham cracker on the lined cookie sheet. Repeat until all crackers are coated, then place in fridge or freezer until chocolate hardens.
Mix together peanut butter, powdered sugar, milk, and vanilla, until smooth. You can use your (clean) hands to mix when this starts to get thick.
Roll peanut butter mixture into into 12 equal peanut butter dough balls and chill for about 15 minutes in the freezer.
Take out the cold chocolate covered graham crackers and peanut butter dough balls. Place one peanut butter ball on top of each graham and press to spread the peanut butter until it fully covers each cracker.
Make another batch of melted chocolate, then spoon it over top of the peanut butter layer. Use enough so that it covers the top and sides completely, to seal the peanut butter inside.
Place crackers back in the fridge or freezer to set (about 15 – 20 minutes).
Drizzle leftover chocolate over the top for decoration, if desired.