Prep the Oven and Pan: Preheat your oven to 200°F (93°C). Lightly grease a large roasting pan with cooking spray (a large disposable aluminum pan works great for easy cleanup). Add the mini pretzels to the roasting pan and set aside.

Boil the Toffee: In a heavy-bottomed medium saucepan, combine the brown sugar, cubed unsalted butter, and light corn syrup. Bring the mixture to a rolling boil over medium heat.

Time It: Once boiling, set a timer and boil for exactly 5 minutes, stirring constantly to prevent the bottom from burning.

Aerate the Toffee: Remove the saucepan from the heat immediately. Quickly whisk in the vanilla extract and baking soda. The toffee mixture will bubble violently and expand—this is completely normal!

Coat the Pretzels: Carefully pour the hot, foamy toffee mixture evenly over the pretzels in the roasting pan. Sprinkle half of the bag of Heath toffee bits over the pretzels as well. Use two spatulas to quickly toss everything together until the pretzels are evenly coated.

Bake: Place the roasting pan in the preheated oven and bake for 1 hour. Important: Remove the pan every 15 minutes to thoroughly stir the pretzels, ensuring the hot toffee mixture coats them evenly as it bakes.

Cool and Set: Once the baking hour is up, immediately turn the hot pretzel mixture out onto a countertop lined with wax paper or parchment paper. Spread them out into an even layer.

Final Garnish: While the pretzels are still hot and sticky, sprinkle the remaining half of the Heath toffee bits evenly over the top.

Break and Serve: Allow the pretzels to set and harden completely (about 1 hour). Once cooled, break them into smaller clusters, serve, and enjoy!