01 - Line two baking sheets with parchment paper or silicone mats to prevent sticking.
02 - In a heavy-bottomed saucepan over medium heat, combine granulated sugar, brown sugar, butter, heavy cream, milk, and salt. Stir constantly until the butter melts and the sugars dissolve completely.
03 - Attach a candy thermometer to the pan. Continue cooking, stirring occasionally, until the mixture reaches 236°F (soft ball stage), about 8–10 minutes.
04 - Remove from heat immediately. Add vanilla extract and pecans. Stir briskly with a wooden spoon for 2–3 minutes, until the mixture thickens and becomes creamy but remains pourable.
05 - Working quickly, drop heaping tablespoons of the mixture onto the prepared baking sheets, spacing them 2 inches apart to allow for spreading.
06 - Let pralines cool at room temperature for at least 20 minutes, until completely set and firm to the touch.
07 - Store in an airtight container at room temperature for up to 1 week. Separate layers with wax paper to prevent sticking.