01 - Line a baking sheet with parchment paper and set aside.
02 - In a large, heavy-bottomed saucepan, combine the granulated sugar, brown sugar, and heavy cream. Stir to blend.
03 - Place the pan over medium heat and stir constantly until the sugars dissolve and the mixture starts to bubble.
04 - Add the butter and stir until melted.
05 - Attach a candy thermometer to the pan. Continue cooking, stirring frequently, until the mixture reaches 238°F (soft-ball stage), about 10-15 minutes.
06 - Remove from the heat. Add the vanilla extract, salt, and pecan halves. Stir vigorously for about 2-3 minutes, until the mixture thickens and becomes creamy but is still pourable.
07 - Quickly drop spoonfuls of the mixture onto the prepared baking sheet, spacing them about 2 inches apart.
08 - Let the pralines cool completely at room temperature until set, about 20-30 minutes.
09 - Store pralines in an airtight container at room temperature for up to 1 week.