Cut the bacon into strips. Peel the celery. Clean and wash the leek. Peel and wash potatoes and carrots. Peel onion. Dice vegetables and potatoes. Heat oil in a large pot, fry bacon in it until crispy.
Fry peas, vegetables, potatoes, onion and bay leaf in the oil, add 1.5 litres of water and bring to the boil. Cover and cook for about 2 hours until creamy.
If the soup is too thick, dilute with water. If it is not creamy enough, puree it gently with a hand blender. Season to taste with marjoram, salt and pepper. Add the sausages to the soup and warm them up.