Coat an 8-inch square baking dish with nonstick cooking spray.
In a large saucepan, bring the butter, heavy cream, granulated sugar, brown
sugar, and salt to a boil over medium heat, stirring frequently. Allow to boil
for 5 minutes, stirring constantly, then remove the pan from the heat.
Stir in the pecans and vanilla extract.
Add the confectioners' sugar and stir until smooth and well combined.
Spread the mixture into the baking dish.
Allow to cool to room temperature then cut into 1-inch squares and serve,
or store in an airtight container until ready to serve.