Preheat the oven to 350°F. Grease a 9×13 inch pan with butter; set aside.
Crust:
In a medium saucepan over medium heat, melt the butter and cook, swirling the pan occasionally, until the butter smells nutty and is golden brown, 3 to 5 minutes. Once you smell that nutty aroma, take the pan off the heat and pour the browned butter into a large heat-proof bowl to cool (about 5 minutes). Set saucepan aside and do not wash!
To the bowl with the brown butter, add the granulated sugar, vanilla and salt; give it a quick stir. Add in flour and combine well with butter mixture. Transfer mixture to prepared pan and press evenly. Bake for 15 minutes.
Filling:
In the same saucepan used to brown the butter, add butter, brown sugar, maple syrup, and heavy cream over medium heat. Whisk until sugar is dissolved and bring to a boil (about 3 minutes)
In a separate bowl, whisk eggs and slowly add 4-5 tablespoons of the hot liquid to temper the eggs. Slowly drizzle tempered eggs with liquid back to the saucepan. Stir well and remove from heat. Add in bourbon and pecans and transfer evenly over the crust.
Bake for 30-35 minutes until the filling is set. Remove from the oven and allow to cool. Wrap in plastic wrap and refrigerate until cold. Cut into bars and serve with vanilla ice cream and salted caramel sauce. Enjoy!
Salted Caramel Sauce:
Heat granulated sugar in a medium saucepan over medium heat, stirring constantly with a high heat resistant rubber spatula or wooden spoon. Sugar will form clumps and eventually melt into a thick brown, amber-colored liquid as you continue to stir. Be careful not to burn. Once sugar is completely melted, immediately add the butter. Be careful in this step because the caramel will bubble rapidly when the butter is added.
Stir the butter into the caramel until it is completely melted, about 2-3 minutes. Very slowly, drizzle in ½ cup of heavy cream while stirring. Since the heavy cream is colder than the caramel, the mixture will rapidly bubble and/or splatter when added. Allow the mixture to boil for 1 minute. It will rise in the pan as it boils. Remove from heat and stir in 1 teaspoon of salt. Allow to cool and transfer to a glass jar.
