1. In a food processor, finely grind the shortbread. You should have 2 cups crumbs. Add the pecans and confectioners' sugar and pulse until the nuts are chopped. Transfer to a large bowl.
2. In a small saucepan, bring the bourbon to a boil. Remove from the heat and add ¾ cup chocolate chips. Stir until smooth. Pour into the pecan mixture and stir until well-combined. Form into sixteen 1½-inch balls.
3. Place the remaining ¼ cup chocolate chips in a resealable plastic bag. Microwave in 20 second increments until melted, squeezing the chocolate in the bag to evenly melt. Snip a small hole in one corner and drizzle the chocolate onto the balls. Refrigerate in an airtight container until firm, at least 2 hours and up to 1 week.