Heat oil over a medium heat in a small frying pan and fry onion and baby marrows until just soft.
Divide mixture between 6 lightly greased, ovenproof cups or ramekins (ceramic bowls). Choose cups or bowls that will fit into a saucepan or frying pan, so that it can be covered with a lid.
Bring 2-3 cm of water in the saucepan to a gentle simmer over medium heat.
Crack an egg into each cup, over veggies and sprinkle with remaining feta.
Carefully place cups in water in the saucepan or frying pan and fill with more boiling water if necessary, so that the cups stand halfway in water.
Cover with the lid and reduce the heat. Simmer gently for 8-10 minutes or until the egg yolks are cooked to your preference.
Serve with black pepper and salad ingredients or a slice of wholewheat toast per person. A small portion of fruit can also be served instead of the salad ingredients.
Any left-over veggies, meat or chicken can be spooned into the bottom of the cups or bowls. Use about 80-100 ml of filling per cup.
Substitute the baby marrow for small broccoli florets or use 125 g mushrooms, sliced.
Left-over or tinned fish will also be delicious. Try tuna with the baby marrows or just spoon pilchards in tomato sauce into the bottom of the cups.Prepare a light meal by using slightly bigger bowls and adding two eggs to each container.