Line 2 large baking sheets with wax paper or silicone baking mats. Set aside.
In a heavy bottomed saucepan melt together butter, brown sugar, granulated sugar with cream and corn syrup. Cook, stirring over medium-high heat just until it comes to a boil.
Immediately lower the heat to medium. Cook until a candy thermometer reaches soft ball stage. (Around 236°F) This may take as long as 20 minutes.
Remove from heat, stir in pecans, bourbon and vanilla. Mix with a wooden or non stick spoon for 1-2 minutes or until it begins to thicken and has a matte sheen. Don't skip this step.
Work quickly with 2 Tablespoons dropping onto wax paper in rounds, forming into even shapes. Use one Tablespoon to drop and the other to scrape the mixture from the spoon.
Let sit until completely dry and set. Store in an airtight container at room temperature.
There's room to adjust the amount of bourbon flavor in these pralines. If you want to a stronger taste of bourbon, add 4 Tbsp. Just a hint of bourbon flavor can be achieved by using 1-2 Tbsp. Adjust to your preference.