1 ½ cups granulated sugar
1 ½ cups packed dark brown sugar
½ cup whole buttermilk
½ cup heavy cream
2 tablespoons light corn syrup
½ teaspoon salt
3 tablespoons cold unsalted butter, chopped into small pieces, at room temperature
2 teaspoons vanilla extract
2 ½ cups pecan halves, toasted
2 tablespoons (1 oz.) bourbon, rum, or Tennessee whiskey
Line 2 baking sheets with parchment paper. (If using paper baking cups, place 16 cups on baking sheet or on a tray.)
Stir together sugars, buttermilk, cream, corn syrup, and salt in a heavy, 2-quart saucepan; attach a candy thermometer to side of pan.
Place pan over low; cook, stirring constantly, until sugars are melted and mixture is smooth, 5 to 8 minutes.
Increase the heat to medium-high, and bring mixture to a boil. Boil gently until the thermometer reaches 230˚F to 235˚F (soft-ball stage), 10 to 12 minutes. Remove from heat; let cool to 220°F, 6 to 8 minutes.
Using a wooden spoon, vigorously stir in butter and vanilla, stirring until mixture turns creamy and opaque.
Stir in pecans and bourbon, and quickly spoon out ¼-cup portions onto prepared baking sheets or into paper baking cups.
Let pralines stand until completely cool, about 1 hour.
Serve immediately, or wrap each praline individually in wax paper or plastic wrap, and store in an airtight container for up to 1 week.