Preheat oven to 200C (400F/Gas 6). Line a large baking tray with baking paper (baking sheet with parchment paper). Cut each slice of bread into 4 small triangles. Put on prepared tray and spray with cooking spray. Bake 10-15 minutes, or until crisp and golden. Leave to cool.
Meanwhile, finely grate zest of oranges and set aside. Remove all skin and pith from oranges. Using a small sharp knife, remove segments from oranges, working over a bowl to catch the juice. Put segments on a plate. Set juice aside.
Heat 1 teaspoon oil in a non-stick frying pan over medium heat. Add a quarter of the livers and cook 1-2 minutes on each side, or until browned and almost cooked through. Transfer to a plate, cover and keep warm. Repeat with remaining livers, cooking for a quarter at a time.
Return all livers to pan. Add orange zest and parsley and toss until combined and heated through, 1-2 minutes. Season with pepper, stir through and remove from heat.
Arrange salad leaves and orange segments on four serving plates. Top with chicken livers and put toast triangles alongside. Whisk remaining oil and reserved orange juice in a jug. Drizzle over individual salads just before serving.
You can buy different combinations of mixed salad leaves in packets at supermarkets and greengrocers.