Line a baking sheet with parchment paper and set aside.

In a small bowl, melt white chocolate at 30 second increments, stirring well to prevent scorching. Once white chocolate is completely melted and smooth, spread on parchment paper into a rectangular shape. Sprinkle chopped pistachios, cranberries and whole M&M's on top. Place in the refrigerator for 10 minutes to set. Break apart into pieces with hands or cut with a knife. Store at room temperature or in the refrigerator.