Line an 8x8 inch pan with aluminum foil or parchment paper and set aside.

In a large bowl, stir together butter and vanilla extract. With an electric mixer on low speed, add in the pretzel crumbs, 2/3 cup peanut butter, and confectioners sugar. Mix until thoroughly combined.

Press mixture into the prepared pan to form an even crust layer.

In a medium microwave-safe bowl, combine chocolate baking chips and peanut butter. Microwave on medium power (50 percent) for 1 minute. Remove and stir. If chocolate is not melted, return to the microwave and repeat the heating step, stirring every 30 seconds to avoid scorching. Stir until smooth.

Using an offset spatula, spread chocolate mixture over the prepared crust layer.

Refrigerate bars for at least one hour before cutting into squares or sticks.