Peel and chop the onion. Celery peel, wash and cut into fine cubes. Clean the leek, cut into thin rings and wash.
Heat the oil in a pot. Sauté the onion for 3-4 minutes. Add celery and leek and fry for about 2 minutes. Add stock, bring to the boil and simmer for 8-10 minutes.
In the meantime cut the slices of bread in half lengthwise. Place the bread strips on a baking tray lined with baking paper. Grate the cheese and spread it on the bread strip. In a preheated oven (electric cooker: 200 °C/ circulating air: 175 °C/ gas: see
manufacturer) bake for approx. 7 minutes
Add peas to the soup, bring to the boil and simmer for about 3 minutes. Remove the pot from the stove, mash the soup coarsely (should still be able to see whole peas). Season to taste with salt and pepper. Wash chives, shake dry and cut into small rolls.
Fill soup into bowls. Sprinkle with chives and add 1 baked piece of bread.