To make pralines (pronounce PRAH-leens), combine granulated sugar, light brown sugar, and evaporated milk in a saucepan. Bring to a boil, stirring often. Brush down any crystals that have formed on the sides of the pan with a brush dipped in warm water.
Cook over medium heat, stirring often, 11 minutes or until a candy thermometer registers 228 degrees.
Stir in toasted pecans and butter, and cook, stirring constantly, until the butter melts and the candy thermometer registers 232 degrees.
Remove from heat, and stir in vanilla.
Beat vigorously with a wooden spoon 1 to 2 minutes or just until mixture begins to thicken and loose its gloss.
Quickly drop by heaping teaspoonfuls onto wax paper. Let the pralines stand about 30 minutes until they’ve completely cooled and are firm.