Freeze blue cheese for at least 8 hours or up to 24 hours. Preheat oven to 325°. Melt butter in a small nonstick skillet over medium-low heat; add chopped pecans, and cook, stirring often, 5 to 7 minutes or until lightly toasted and fragrant. Place popcorn in a 15- x 10-inch jelly-roll pan. Grate frozen cheese to equal 1 cup. Sprinkle 1 cup grated blue cheese over popcorn. Toss popcorn mixture with toasted pecans and pepper. Bake at 325° for 10 minutes. Serve immediately.