Preheat the oven to 350°F. Line a baking sheet with parchment paper. Add pecans to the baking sheet and bake for 7-9 minutes. Set aside to let cool. Line two baking sheets with parchment, set aside.
In a medium pot over medium heat, combine together granulated sugar, brown sugar, salt, evaporated milk, and butter. Stir constantly until the sugars are dissolved.
Continue cooking at a steady boil until the candy thermometer reaches 230°F.
Add in the toasted pecans and stir constantly with a wooden spoon until the candy thermometer reaches 235°F - 240°F.
Remove the pot from the heat and pour in vanilla. DO NOT STIR, let the mixture cool down to 212°F.
Set a timer and stir at a steady, brisk pace for 1-2 minutes, just until it starts to thicken and loses some of its gloss (it will look a little matte).
Working quickly, drop heaping spoonfuls onto the prepared baking sheet. If the mixture starts to get too thick, stir in a teaspoon of hot water.
Let the pralines sit at room temperature until they are set, about 25 minutes.