Preheat oven to 375°F. Line an 8x8 baking dish with parchment paper. Set aside. In a food processor, add in flour, milk, vanilla extract, and cold butter that’s been cubed and pulse for a few seconds. Next, add in salt, egg yolk and sugar. Pulse until everything is well blended together.
Pour dough mixture into baking dish. Form dough crumbles into one ball and then press into the baking dish with your hands and the bottom of something flat, like a measuring cup. This will help get the dough texture as smooth as possible. Poke a few holes into the dough with a fork. Bake crust at 375° for 20 minutes or until golden.
Filling
Melt together butter and maple and corn syrup in a pot for about 2 minutes on medium heat. Lower temperature then stir in cornstarch and sugar. Turn off once combined and sauce has thickened. Remove from heat. Let cool for a few minutes.
Whisk eggs and vanilla in a large bowl. Slowly, add syrup and butter mixture to egg mixture and whisk together as you’re pouring it in. Fold in pecans. Pour over crust and bake at 350° for 35 minutes. Let bars completely cool to room temperature before cutting and serving. Keep bars stored in the refrigerator in an air-tight container.