In a large frypan heat oil over medium high heat. Add onion and saute until translucent. Add thyme, basil, parsley and season with salt and pepper to taste. Add sherry then reduce heat to medium low and let all simmer.
Meanwhile, cut liver into small pieces about the size of large sugar lumps then add to the frypan mixture. Cook all together shaking frypan well for 6 to 7 minutes. Add more sherry if mixture gets dry. Garnish with fresh diced parsley and fried croutons and serve.
To make croutons drizzle olive oil over cubes of bread, toss to coat all sides. Cook croutons in a frypan over medium heat until golden brown.