To a large mixing bowl add peanut butter, powdered sugar, peanut butter powder and butter. Blend mixture on low to start bring together then increase to medium and blend until combined. If needed you can thin it with a little more peanut butter or thicken with powdered sugar, it should feel like a pretty stiff cookie dough and shouldn't be runny or sticky.
Line two baking sheets with parchment paper. Scoop out 1 even teaspoon at a time and roll into balls. This process will go faster if you've got someone to help, one person scoops the other person rolls.
Place peanut butter ball over 1 pretzel then smash a second pretzel over the top. Place them on the baking sheet.
Refrigerate until filling is fairly firm, about 30 to 60 minutes.
Place chocolate chips in a medium microwave safe bowl along with the vegetable oil. Heat in microwave on 50% power in 30 second intervals. Stir well between each until chocolate is melted. Note that the last time heating you may only need 15 seconds or so, careful not to overheat it or it can seize.
Remove one baking sheet of the peanut butter stuffed pretzels from fridge. Dip the pretzels halfway in the chocolate then remove and shake and scrape excess chocolate underneath off along the side of the bowl.
Cover with sprinkles if using.
Melt white chocolate in a microwave safe bowl in the microwave on 50% power in 30 second intervals stirring well between each until melted and smooth.
Repeat dipping process with white chocolate and cover with sprinkles. Transfer to fridge for chocolate to set, about 15 minutes.
Notes
*I found I liked these quite a bit more with the addition of peanut butter powder for a more pronounced peanut butter flavor. If you don't have it you can just add in another 1/2 cup powdered sugar just note they'll be sweeter and have a bit less peanut butter flavor.
Store peanut butter pretzel bites in the fridge for up to 2 weeks.