Preheat your oven to 175°C (350°F). Line your 9-inch square pan with parchment paper, leaving some overhang for easy removal.
In a mixing bowl, combine the flour, salt, and brown sugar. Mix them together until evenly distributed.
Add the cold, small pieces of butter into the dry ingredients. Use your fingers or a pastry cutter to work the butter into the flour until the mixture resembles coarse crumbs.
Press this crumbly mixture firmly into the bottom of your prepared pan to form an even crust. Bake for about 15 minutes until golden around the edges.
While the crust bakes, toast the pecans in a dry skillet over medium heat for about 5 minutes, stirring frequently until fragrant and darker in color. Let cool, then coarsely chop them.
In a saucepan over medium heat, combine the maple syrup, brown sugar, and butter. Bring to a gentle boil and simmer for 5 minutes, stirring occasionally. Remove from heat and stir in vanilla extract.
Coarsely chop the toasted pecans and stir them into the warm syrup mixture, coating them evenly.
Pour the pecan-maple filling over the baked crust, spreading it out evenly with a spatula.
Bake the assembled bars for another 20-25 minutes, until the filling is bubbling and the pecans are caramelized around the edges.
Remove the pan from the oven and allow the bars to cool completely in the pan on a wire rack, about 2 hours. This helps the filling set and makes cutting easier.
Use a sharp knife dipped in hot water to cut the cooled bars into squares, wiping the knife dry between cuts for clean slices.
Serve these bars at room temperature or slightly warmed, enjoying the crunchy, gooey, and caramelized layers with a cozy aroma filling the room.
