In a food processor, pulse chocolate sandwich cookies, cream cheese and peppermint extract until smooth. Chill until firm. Shape into twelve 2-inch ghost shapes. Transfer to a wax paper-lined pan; chill until firm. Chop white chocolate. Microwave two-thirds of it at 50% power, stirring every 30 seconds, until smooth. Stir in remaining chocolate to melt. Pour over ghosts, using a knife to evenly coat. Chill to set. Using a toothpick, poke holes for eyes and mouths.