Preheat oven to 400F. Line 12 standard-size muffin cups with paper liners. Combine muffin mix, milk, cottage cheese and eggs in large bowl. Using electric mixer, beat until well combined. Mix in cheddar cheese. Let stand 5 minutes. Spoon batter into prepared cups, dividing equally. Bake until muffins are brown on top and tester inserted into center comes out clean, about 30 minutes. Let muffins cool to room temperature.