1 bag of microwave popcorn (lightly salted), about 6 cups of popcorn
1 bag of marshmallows (40 large)
1⁄4 cup unsalted butter
1⁄3 cup toasted nuts, optional (or other dried fruits, like cranberries or pistachios)
1. Spray the cake pan with oil. Set aside. Cook the popcorn and transfer to a large bowl. In a large saucepan over medium-low heat, place the butter and melt; add the marshmallows and stir briefly from time to time until they melt, combining them with the melted butter. Immediately pour onto the popcorn and fold quickly with a spoon to coat as many popcorns as possible with the sauce. Transfer to the cake pan and using a piece of plastic (otherwise the texture is too sticky), press on the popcorn cake to make it adhere to the pan and to give it shape.
2. Place in the fridge for about one hour (or longer); to unmold onto a platter, dislodge using a spatula and flip it over and tap on it. It should come out easily