Coat an 8-inch square baking dish with nonstick cooking spray.
In a heavy saucepan - bring the butter, heavy cream, brown sugar, white sugar, and salt to a boil over medium heat, stirring frequently. Allow to boil for 5 minutes, stirring constantly. Remove pot from the heat.
Stir in the pecans and vanilla. Add the confections' sugar and stir until smooth. Spread the mixture into the baking dish.
Allow to cool to room temperature then cut into 1-inch squares. Store in an airtight container.