Preheat the oven to 160°C fan. Lightly spray a non-stick 12-hole, square muffin tray with low-calorie cooking spray. Place inside a roasting dish or deep baking tray.
Divide the potato and spring onion evenly between the muffin tray.
Top the potato and onions with the cheddar.
Crack the eggs into a food processor, add the cottage cheese, mustard, and salt and pepper. Blitz until smooth and no white specks remain. If the mix looks grainy, blitz some more. This will ensure you have a smooth and creamy bake.
Pour the egg mix into the muffin tray and use the end of a spoon to gently swirl the mix together with the filling. As you do this, the contents may settle, so if you have any egg mix remaining, use it to top-up.
Boil the kettle and place your roasting dish in the oven. Create a water bath by pouring boiling water inside the dish, until it comes about halfway up the sides of the muffin tray.
Close the oven door and cook for 25 minutes, until the tops of the egg bites are firm to touch.
Remove from the oven, being careful to not spill any hot water. Then remove the muffin tray from the water bath and let it stand for 5 minutes. If the bakes have puffed up in the oven, they will deflate — this is normal.
Remove the bakes from the muffin tray and serve warm, or cool completely and store in a container in the fridge to eat chilled.