Preheat oven to 325 degrees. Line the bottom and sides of a 9 x 13 inch baking pan with foil, leaving two inches hanging over the edge, and spray lightly with nonstick cooking spray.
Combine butter, sugar, cocoa, and salt in a microwave safe bowl. Microwave in one minute intervals, stirring in between, until smooth. Set aside and let cool until warm to the touch (not hot).
Stir in vanilla. Add eggs one at a time, mixing well after each one. Continue to mix and add flour until well blended.
Spread batter evenly in lined pan.
Melt peanut butter in a small bowl in the microwave, until pourable (about 30 seconds to 1 minute).
Drizzle the peanut butter over the brownies and swirl into brownie batter using a butter knife.
Sprinkle on pretzels, chocolate chips, and toffee.
Bake for 22-25 minutes until set. Let cool completely before serving.