Crush the ladyfinger biscuits into fine crumbs using a food processor.
Mix instant coffee powder with warm milk until dissolved.
In a bowl combine mascarpone cheese powdered sugar and vanilla extract.
Add biscuit crumbs and coffee mixture into the mascarpone mixture and mix well.
Fold in dark chocolate chips if using.
Refrigerate the mixture for 30 minutes to firm up.
Scoop small portions and roll into bite-sized balls.
Coat each truffle with cocoa powder evenly.
Chill the truffles for another 30 minutes before serving.