Finely chop the carrot, onion, garlic, and celery.
Heat a little olive oil in a medium pan and gently cook the vegetables until softened.
Add the sliced bell pepper, herbs, and shiitake mushrooms. Cook for about 5 minutes, until the mushrooms have softened and reduced slightly.
Add the chopped tomatoes, then fill the tin with water and pour it in - enough to just cover everything.
Add the stock cube, bring to a boil, then simmer for about 10 minutes.
Meanwhile, cut the duck liver into small pieces.
Add the liver to the sauce, cover, and cook for 3–5 minutes until just cooked through.(Avoid overcooking, as it can become tough.)
Taste and adjust seasoning if needed.
Serve hot with your choice of pasta, mashed potatoes, rice, or buckwheat, and finish with chopped parsley.