Spray a 9x13 pan with cooking spray. Cut a piece of parchment paper to fit the bottom of the pan. Place it in and spray the top with cooking spray.
In a mixing bowl, add in butter and sugar. Mix on medium until completely combined. Scrape down the bowl and mix in any remaining butter or sugar.
Add in the egg and vanilla. Mix on medium until well incorporated. Scrape down the sides of the bowl.
Add in all of the flour and mix on low so the flour doesn't go everywhere. Once the flour is mostly incorporated, turn the mixing on medium and mix until flour is combined. If the dough doesn't come together completely, add in a teaspoon to two teaspoons of milk and mix again. The dough should come together.
Press the dough into the bottom of the pan. Make sure you get all the corners and edges.
Place the crust in the oven for 20 minutes. The edges will start to brown up.
As soon as the 20 minutes are up, have the pecan pie filling ready to go on the crust.
Pecan Pie Filling
In a medium sized bowl, add in all of the ingredients and whisk until combined.
As soon as the crust comes out, pour the filling in and put back in the oven.
Bake at 350 for 32-35 minutes or until done. Let the bars cool completely before slicing. Slice and eat.