Heat oven to 425°F. Spray 12 regular-size muffin cups with cooking spray, or line with paper baking cups and spray paper cups.
In medium bowl, mix milk, buttermilk, margarine and egg; blend well.
In large bowl, mix flour, cornmeal, sugar, baking powder, baking soda and salt.
Push dry ingredients aside to form well in center. Add milk mixture; stir just until dry ingredients are moistened. Spoon batter evenly into muffin cups, filling each 2/3 to 3/4 full. Press 1 cheese cube into center of each.
Bake 10 to 15 minutes or until golden brown and firm to the touch. Immediately remove muffins from pan. Cool slightly. Serve warm.