Preheat the oven to 200C/400F/Gas 6.
For the soup, heat the oil in a pan over a medium heat. Fry the onion and garlic for 2-3 minutes, stirring occasionally, until softened.
Add the leek to the pan and cook for two minutes. Add the stock, bring to the boil, then reduce the heat until the mixture is simmering. Simmer for 4-5 minutes.
Stir the spinach into the mixture until wilted. Add the nutmeg. Season with salt and freshly ground black pepper, to taste.
Blend the soup mixture until smooth with a hand-held blender.
Meanwhile, for the cheese croûte, bake the bread on a baking tray in the oven for 3-4 minutes. Top with the grated cheddar and return to the oven for a further 3-4 minutes, or until the cheese is melted and golden-brown. Cut in half.
To serve, pour the soup into a bowl, float the two croûtes on top and float the poached egg in the centre between the croûtes.
