In a large microwave-safe bowl, combine the brown sugar, butter, corn syrup and molasses. Microwave, uncovered, on high for 45-50 seconds or until the butter is melted; stir.
Microwave 15-25 seconds longer or until mixture boils. Immediately stir in the salt, baking soda and extract (mixture will foam).
Stir in pretzels and peanuts. Microwave on high for 20-30 seconds or until pretzels and nuts are well coated, stirring twice.
Spread into a greased 15-in. x 10-in. x 1-in. pan. (If I use unsalted peanuts, I sprinkle some extra sea salt on the top of the mixture). Cool for 15 minutes, stirring twice. Store in an airtight container.