In a medium bowl, combine pecans, walnuts, and bourbon. Cover and refrigerate for at least 8 hours or overnight to let the flavors meld.

Drain nuts well and pat dry. In a clean bowl, beat butter until creamy. Gradually stir in 2 cups of powdered sugar, then fold in bourbon-soaked nuts until evenly combined.

Using a small cookie scoop or spoon, roll the nut mixture into 1-inch balls. Place on a parchment‐lined tray and chill for 1 hour.

Roll chilled balls in remaining powdered sugar, then return to the tray and refrigerate another 30 minutes.

Melt semisweet chocolate chips (and oil if needed) in a double boiler or microwave, stirring until smooth. Dip each bourbon ball into chocolate, letting excess drip off, then place back on parchment.

Refrigerate until chocolate is firm, about 30 minutes. Store bourbon balls in an airtight container in the fridge for up to 2 weeks.