01 - Line a large baking sheet with parchment paper or a silicone baking mat. Arrange graham cracker pieces in a single even layer, making sure edges are touching.
02 - In a medium saucepan over medium heat, melt the butter. Add the brown sugar, maple syrup, vanilla extract, and kosher salt. Bring to a gentle boil while stirring constantly, then simmer for 2 to 3 minutes until the mixture thickens and turns glossy.
03 - Pour the hot caramel evenly over the graham cracker layer, spreading gently with a spatula to cover all pieces.
04 - Scatter the chopped toasted pecans evenly over the caramel layer. Bake in a preheated oven at 350°F for 8 to 10 minutes, until the caramel is bubbling.
05 - Remove from the oven and immediately sprinkle chocolate chips evenly across the surface. Let rest for 3 to 4 minutes so the residual heat melts the chocolate, then spread it into a smooth, even layer using an offset spatula.
06 - Optionally sprinkle with flaky sea salt. Allow the bark to cool completely at room temperature, or refrigerate for faster setting.
07 - Once fully set, break the bark into irregular pieces. Store in an airtight container at room temperature for up to 1 week.