Chop finely onion, parsley and celery. Put the ham hock, vegetables and half of the peas in a large saucepan with a thick bottom. Pour in 2.5 liters of cold water, cook under medium heat and bring to a boil. Carefully skim off the foam. Do not salt! Boil the soup for 30-40 minutes, pour in the remaining peas, add thyme and wine. Cook for 2.5 hours. If the soup becomes too thick, you can pour in some cold water. Salt and pepper the soup. Remove sprigs from thyme. Before serving, carefully remove the ham hock, clean it with a spatula and cut the meat into small pieces. Put the meat on plates, pour in the soup and serve very hot.