Pick all the chicken meat off the bones and throw away all the skin, bones and bits you don’t want. Chop up the chicken finely and put it in a bowl.
Melt half the butter in a small pan and sauté the onion over medium–low heat until it is soft and lightly golden. Add the celery, parsley and garlic and, when you can smell the garlic, add the tomato. Simmer until it has totally melted, squ