Preheat the oven to 350°F. Line a 9x13 pan with parchment, leaving an overhang.
Whisk flour, brown sugar and salt. Cut in butter until it looks like coarse crumbs. Stir in discard until a crumbly dough forms.
Press evenly into the pan, prick with a fork and bake 18 to 20 minutes until the edges are light golden.
Whisk eggs, brown sugar, maple syrup, melted butter, flour, vanilla and salt until smooth. Stir in pecans.
Pour over the warm crust and bake 25 to 30 minutes, until the edges are set and the center barely jiggles.
Cool completely, chill at least 1 hour, then cut into 24 bars.