Preheat the oven to 180°C, gas mark 4. Sauté the spring onion in 1 tsp of oil until soft. Add the spinach and sauté for a further minute, then leave aside to cool in a large bowl.
Place the shallots into a medium-sized frying pan with the remaining olive oil, pinch of salt,and sugar and sauté over a gentle heat until slightly caramelised.
Place the toasted California walnuts into a food processor and blitz until coarsely chopped.
Next, add the chopped herbs, nutmeg and eggs to the large bowl with the spinach, season with black pepper and stir to combine.
Brush a 20cm x 30cm baking tray with butter and line with three layers of filo, brushing with butter in between each of the layers. Spread over half the caramelised shallots, followed by half the spinach mixture, half the feta and a third of the California walnuts.
Repeat the layers using the remaining fillings, reserving a third of the California walnuts.
Finish with a final 3 layers of buttered filo, trimming the final layer to fit the dish. Brush the top with butter and score, sprinkling with a little water.
Place in the oven and bake for 25-30 minutes, or until golden brown and crispy. Sprinkle with the remaining California walnuts and drizzle with honey to serve.