01 - Line a large baking sheet with parchment paper or a silicone baking mat. Arrange graham cracker pieces in a single even layer, with edges touching to form a continuous surface.
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, stirring constantly, and 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 carefully with a spatula to cover all edges.
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 across the surface.
05 - Remove from the oven and immediately scatter the chocolate chips evenly over the top. Let sit for 3 to 4 minutes until softened, then spread into a smooth, even layer using an offset spatula.
06 - Sprinkle lightly with flaky sea salt if desired. Allow 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.