Grease 2 baking sheets; set aside. In a large heavy saucepan over medium heat, melt butter. Stir in the sugars, then cream; cook and stir until mixture comes to a boil. Cook, stirring occasionally, until a candy thermometer reads 236° (soft-ball stage), about 20 minutes.
Remove from the heat; stir in the pecan halves, chopped pecans and bourbon. Immediately drop by tablespoonfuls onto prepared baking sheets. Let stand until pralines are set and no longer glossy. Store in an airtight container.
We recommend that you test your candy thermometer before each use by bringing water to a boil; the thermometer should read 212°. Adjust your recipe temperature up or down based on your test.