Cut the bread into small cubes, spread out on a baking tray and toast in a preheated oven at 180°C (160°C fan, gas 4) for 10 minutes. Remove and allow to cool.
Wash the celery and reserve the leafy tops. Halve the leeks lengthways and wash well. Cut the celery and leeks into 5mm pieces or strips.
Melt the butter in a saucepan. Whisk the eggs and milk and mix with the toast cubes and melted butter. Stand for 15 minutes.
Wash the chives, shake dry and finely chop, then add to the bread mixture. Season with salt, pepper and some freshly grated nutmeg. Stir in the flour.
Bring a large pan of salted water to the boil. Reduce the heat so that the water is only just bubbling. Shape the bread mixture into 8 dumplings with damp hands and add to the pan. Let the dumplings cook for 12 minutes over a low heat.
Meanwhile, heat the oil in a pan and fry the celery and leeks briefly. Pour in the vegetable stock and add the frozen spinach. Cook, covered, overa low heat for 6-8 minutes.
Toast the pumpkin seeds in a dry pan until lightly browned.
Add the peas to the vegetables in the pan. Season with salt and pepper and cook for another 3-5 minutes. Coarsely chop the celery greens.
Season the vegetable mixture with freshly grated nutmeg. Remove the dumplings from the pan, drain and serve with the vegetables. Garnish with celery greens and pumpkin seeds.