Finely chop the white chocolate. In a medium bowl, microwave half of the chocolate at 50 percent power in 30-second intervals, stirring between intervals, until melted, about 2 minutes. Add the remaining chocolate and stir until completely melted. Stir half of the cereal and all the nutmeg into the chocolate. Using a silicone or offset spatula, spread the chocolate evenly (about 1/4 inch thick) onto a parchment paper-lined baking sheet. Sprinkle with the remaining cereal, cookies, sprinkles, and nonpareils. Chill until set, about 30 minutes. Cut into irregular pieces.
The Do's and Don'ts of Cooking with Chocolate