Preheat oven to 300 degrees F. In a large roasting pan, stir together cereal and nuts; set aside.
In a small saucepan, stir together brown sugar, corn syrup, butter, cinnamon, and ginger. Cook and stir over medium heat until butter is melted and mixture is smooth. Pour over cereal mixture; stir gently to coat.
Bake in the preheated oven for 30 minutes, stirring twice. Remove from oven. Spread mixture on a large piece of buttered foil to cool. Break into pieces. Stir in chocolate-covered raisins and the chocolate pieces. Store in an airtight container for up to 1 week. 16 cups (32 servings)