Preheat the oven to 350 degrees F. Line a 9"x13" pan with parchment paper. Coat the pan with cooking spray.
In a large bowl using a mixer, beat together 1 cup of the butter and 1/2 cup of the brown sugar until light and fluffy, about 3 minutes.
Add 1 1/2 teaspoons of vanilla extract and 1 tablespoon of water, then mix until combined. With the mixer on low speed, add the flour and mix until coarse crumbs form.
Scoop the dough into the pan. Use your fingertips to press the dough evenly into the pan. It helps to use an offset spatula coated with cooking spray to get an even layer.
Bake for 15 minutes, until crust is lightly browned around the edges.
Melt the butter in a large saucepan over medium-high heat. Add the remaining 1 1/2 cups of brown sugar and the corn syrup. Stir until well blended.
Bring to a boil and stir frequently for 3 minutes. The mixture will get light and airy. Remove the pan from the heat and add the heavy cream and the remaining 1 1/2 teaspoons of vanilla extract. Stir until combined.
Add the pecans and stir until they are completely coated.
Pour the pecan mixture over the crust, and spread into an even layer.
Return the pan to the oven and bake for 25 minutes, until the pecan topping is set (it will move slowly when you wiggle the pan).
Allow the bars to cool completely before cutting into squares.