1. Line a baking sheet with parchment paper. Crush Oreo cookies into medium-sized pieces. A food processor or a Ziploc bag with a rolling pin works great. Melt the white chocolate in a microwave-safe bowl in 30-second intervals, stirring until smooth. Be careful not to overheat. Stir about half of the crushed Oreos into the melted white chocolate. Pour the mixture onto the prepared baking sheet and spread evenly, about 1/4 inch thick. Immediately sprinkle the remaining crushed Oreos and all of the Halloween sprinkles over the top of the melted chocolate. Refrigerate for at least 30 minutes, or until the bark is completely set and firm. Break the bark into irregular pieces. Store in an airtight container at room temperature or in the refrigerator for up to a week.