Cook the spinach leaves in the butter over a low heat until soft. Chop coarsely and leave to cool. Cut out small ‘U’-shaped channels along the length of the courgette/zucchini. Boil it for 3-4 minutes in a little salted water. Drain and cool. Slice into 5-mm/¼-inch pieces shaped like cog wheels. Purée the spinach with its liquid and add the eggs, cheeses and seasoning. Pre-heat the oven to 200°C/400°F/Gas mark 6. Generously butter a 1.2-litre/2-pint/5-cup terrine or loaf pan and pour in about 1 cm/½ inch of the cabbage and coriander purée. Into this stand some of the courgette/zucchini cog wheels, well spaced, in any pattern you choose. Cover with a layer of spinach purée, then another layer of the cabbage and coriander. Arrange a few more courgette/zucchini pieces in different places. You should be able to get in six layers altogether. Cover with buttered greaseproof/waxed paper and cook in a bain marie for 40-45 minutes. Let the terrine rest for 10 minutes before unmoulding. Then refrigerate for 2-3 hours or 1 day.