Preheat the oven to gas 4, 180° C, fan 160° C.
Using a rolling pin, flatten each of the bread slices. Spread both sides of each slice with butter and press each into a recess on a muffin tin.
Crack an egg into the centre of each bread case. Sprinkle with the chopped spring onion and grated cheese
Bake in the preheated oven for about 18-20 minutes, until the eggs have just set.
Obviously these take a bit of time to make, so get everything ready the night before and break the eggs and cook the tarts while you're in the shower and getting dressed. To ring the changes you can also sprinkle some chopped bacon or ham into the muffin bread case before you add the egg.
*Inspired by Kerry-Lee E. featured in the Realfood Cookbook