Heat oven to 350 degrees. Line a 13x9-inch pan with parchment or greased foil overlapping the long sides to be able to lift out the bars when baked.
Toast the pecans: spread on a cookie sheet and bake for 5 minutes, watching carefully so they don't burn. Chop all coarsely and set aside.
Make Crust: In a food processor pulse the flour, 1/3 cup sugar, 3/4 cup pecans and 1/4 teaspoon salt until combined. Cut a cube of butter (1 cup) into 8 pieces and add to bowl of processor. Pulse 8-10 times until mixture resembles coarse meal.
Press crust mixture evenly into the prepared pan. Bake 20-25 minutes until lightly browned at edges and remove to a wire rack to cool for 20 minutes.
While cooling, immediately sprinkle warm crust with chocolate chips; leave for a few minutes to soften and then spread into an even layer.
Make Filling: When about 10 minutes is left on the timer for the cooling, add maple syrup, 1/2 cup sugar, cream, 6 tablespoons butter, and 1/4 teaspoon salt to a large saucepan and bring to a boil over medium-high heat. Stirring constantly, boil for 1 minute.
Remove from heat, add the remaining chopped pecans and vanilla, and pour over crust.
BAKE 14-15 minutes until the filling is bubbly. Remove to a wire rack and cool for about 1 hour. Refrigerate another hour before cutting into 24 pieces.
Store in an airtight container in the fridge until serving or freeze for longer storage.