How to Make It
Spray a baking sheet with cooking spray or line with greased parchment paper. Arrange the crackers on the prepared pan in a single layer, breaking them to fit if need be.
Stir the sugar, butter, and syrup in a large saucepan over medium-low heat until the sugar is melted. Brush the side of the pan with a moistened pastry brush to wash down any sugar crystals. Insert a candy thermometer. Cook the syrup over medium heat without stirring until it starts to brown around the edge. Continue simmering, carefully swirling the pan occasionally, until the temperature registers 300° F.
Slowly and carefully pour the caramel over the crackers, then spread with an offset spatula into an even layer completely covering the crackers. Let cool for 2 minutes, then sprinkle the chocolate on top. Let stand until the chocolate starts to melt, then spread the chocolate evenly over the toffee. Sprinkle the pumpkin seeds and cacao nibs evenly over the chocolate. Freeze the toffee until set, about 15 minutes.
Invert the toffee onto a work surface and peel off the parchment, if using. Invert again and break into large shards.
Storage tip: The toffee can be refrigerated for up to 2 weeks in an airtight container.