1. Cut potatoes into 2cm cubes.Boil, steam or microwave until just tender,drain.
2. Heat oil in a large non stick pan, cook bacon and onion until onion is soft. Add potatoes stir till browned slightly. Add spinach until just wilted.
3. Whisk eggs and milk in large bowl.
4. Pour egg mixture into pan, cook tilting, over medium heat until egg is almost set.
5. Sprinkle frittata with cheese and place under grill until cheese is melted and browned lightly.