Melt 6 tablespoons butter in a large pot over medium heat. Stir in one 10-ounce bag mini marshmallows until melted, then stir in 1 teaspoon vanilla; remove from the heat. Stir in 7 cups cinnamon cereal squares and 1 1/2 cups crushed freeze-dried apples. Press into an oiled foil-lined 9-inch baking dish. Let cool. Cut into squares.