Place the sugar, corn syrup, water, butter, salt, and butter flavoring in a medium pot and stir to combine.
Bring the mixture to simmer over medium heat. Place a lid on the pot for one minute, and then remove the lid. This will steam any sugar crystals that have formed on the sides of the pot and allow them to slide back down into the mixture.
Place a candy thermometer into the pot and continue to cook on medium heat, stirring frequently until the candy reaches the soft crack stage.
Add the pecans, stir to combine, and continue to cook until mixture reaches the hard crack stage.
Remove the pot from the heat and add the baking soda (the mixture will foam). Make sure you blend baking soda into candy completely.
Pour the mixture onto a nonstick cookie sheet or lightly buttered baking sheet.
Working quickly, spread the mixture out until it is 1/4 inch thick (or thinner). The candy will start to harden quickly.
When the candy has cooled and set, break it into pieces and store it in airtight container.