Place two dish towels on the counter and cover each with a large piece of parchment paper or use silicone mats. Measure out all ingredients before beginning.
Put cold water and a couple of ice cubes in a small bowl & set aside to test the candy to determine if it has reached the soft ball stage. Or have a candy thermometer on hand.
Using a heavy gauge pot, heat heavy cream and stir in the sugars & salt. Stir constantly.
When candy is about 238°, remove from the heat. (Another way to test if the candy is at the Soft Ball Stage, drizzle a little bit of the candy in the bowl of cold water with ice. It is ready when it forms a ball and is soft to the touch.)
Add butter and vanilla and mix well. Caution: the vanilla will sizzle in the candy.
Add the pecans and continue to stir until the candy becomes creamier and opaque as it starts to thicken.
Quickly and carefully spoon the candy onto the parchment paper. Allow to cool and set thoroughly before eating.
Store in an airtight container. Makes about two dozen 2-inch pralines.