Using a food processor, grind cookies to a fine powder. With a mixer, blend cookie powder, cream cheese and vanilla extract until thoroughly mixed (there should be no white traces of cream cheese).
Roll into small balls and place on wax-lined cookie sheet. Refrigerate for 45 minutes.
Line two cookie sheets with wax paper. In double-boiler, melt milk chocolate. Dip balls and coat thoroughly. With slotted spoon, lift balls out of chocolate and let excess chocolate drip off. Place on wax-paper-lined cookie sheet.
In separate double boiler, melt white chocolate. Using a fork, drizzle white chocolate over balls. Let cool.
Store in airtight container, in refrigerator.
Note: When I am exceedingly lazy (most often the case these days), I forego the chocolate 'dip' and merely roll my truffles into various mixtures - chopped nuts, chocolate sprinkles, vari-coloured candy sprinkles, cocoa powder, chocolate shavings, coloured sugars -- still pretty -- less work.