1. Separate the leaves from the stalks of the cavolo nero and chard. Finely chop the stalks and shred the leaves.
2. Finely chop the onion.
3. Heat 2 tbsp of olive oil in a pan and sauté the chopped stalks and onion for a few minutes. Add the orange juice, reduce the heat to medium, and cook for around 20 minutes until the stalks soften.
4. Add the shredded leaves, cinnamon, orange zest, salt, and pepper. Stir until the leaves reduce in size by half. Remove from heat, add the orange blossom honey, and set aside to cool.
5. Whisk the eggs with a pinch of salt and stir in most of the shredded Mahón cheese (reserve about 20g for later). Mix the greens and 40g of toasted pine nuts into the egg and cheese mixture until well combined.
6. Preheat the oven to 180°C.
7. Brush a 23cm springform tin with olive oil. Brush each sheet of filo pastry with oil and layer them in the tin, turning the tin so the pastry covers the sides and base.
8. Add the filling to the tin and sprinkle the reserved cheese and pine nuts on top. Fold the overhanging pastry edges over the filling, scrunching them to form an edge.
9. Bake for 25-30 minutes at 180°C, or until the filo is golden. If the pastry browns too quickly, cover lightly with parchment paper.
10. Let the pie rest for 5-10 minutes before serving to allow the filling to set.

Notes:

• To avoid a soggy bottom, drain the greens thoroughly. You can blanch the cavolo nero first and then the chard, drain, and squeeze out excess water before chopping. Alternatively, drain the mixture in a fine sieve after cooking.
• If you'd like a firmer filling, try using 2 eggs instead of 3.