Preheat oven to 325°F (163°C) and line a muffin tin with 12 paper liners.
Mix cookie crumbs and melted butter in a bowl until well combined. Divide evenly among liners and press down firmly.
In a large bowl, beat cream cheese until smooth. Add sugar, Irish cream, and vanilla, and beat until combined.
Add eggs one at a time, mixing on low speed just until blended.
Divide filling evenly over crusts and smooth the tops.
Bake for 18–22 minutes or until centers are just set.
Cool in pan for 10 minutes, then transfer to a wire rack to cool completely. Refrigerate at least 2 hours before serving.
For ganache: Heat cream until simmering, pour over chocolate, let sit for 2 minutes, then stir until smooth. Spoon over chilled cheesecakes if desired.