To make the crust:
Preheat oven to 350°. Grease a 9- or 10-inch springform pan.
Combine pretzels, melted butter, and brown sugar until well mixed.
Transfer mixture to prepared pan. Press evenly into bottom of pan.
Bake for 10 minutes. Then, set aside to cool slightly.
To make the cheesecake filling:
Place cream cheese, brown sugar, and sour cream in a large mixing bowl or the bowl of a stand mixer. Using a handheld or stand mixer on medium speed, beat until smooth. Mix in vanilla extract.
Add eggs, one at a time, beating well after each addition. Add peanut butter and mix thoroughly.
Pour filling into crust. and spread evenly.
Bake for 15 minutes.
Reduce oven temperature to 200°. Bake for 2 hours, or until the center is firm and the cheesecake no longer looks shiny or wet.
Remove cheesecake from the oven and run a knife around the edge of the pan.
Turn off the oven. Place the cheesecake back into the oven for 2 hours. Then, remove the cheesecake, cover, and chill overnight.
To make the topping: **
Place chocolate and butter in a microwave-safe bowl. Heat in microwave at half-power in 30-second increments until the butter has melted and the chocolate melts when stirred.
Use a spoon to drizzle the chocolate over the chilled cheesecake.
Sprinkle the toffee bits over the top of the cheesecake