Reserve 1-2 Tablespoons Oreo crumbs if using them to decorate. Mix the rest of the crumbs with the cream cheese until well blended.
Shape the mixture into 42 1-inch balls, placing them on a waxed paper lined baking sheet. Freeze the balls while preparing the chocolate.
In a double boiler (or in a heatproof bowl set above a pot of simmering water), add the chocolate and stir frequently until melted.
For colored candy melts, follow package directions for achieving a dip-able consistency. This may involve adding a bit of vegetable shortening to the melts, especially if you are adding extra food coloring.
Remove the cookie balls from the freezer. Add a few balls at a time to the melted chocolate and roll them around with two forks. Remove the truffles with forks and allow excess chocolate to drip back into the bowl before placing truffle back on waxed paper lined baking sheet.
As soon as the truffles have been dipped, sprinkle with remaining cookie crumbs, if using, so they will stick before the chocolate has set. If drizzling with chocolate decoration, the truffles can all be dipped before preparing the drizzle.
To make a drizzle, melt the white chocolate or candy melts carefully in the microwave in 30-second intervals at 50% power. Transfer the melted chocolate to a resealable sandwich bag and snip off the corner. Alternatively, use a pastry bag with a small round tip.
Refrigerate 1 hour or until firm. Store in a tightly covered container in the refrigerator.