Preheat oven to 180°C. Lightly spray a medium baking dish. Set aside.
Cook potatoes in a saucepan of boiling water for 8-10 minutes or until just tender, adding broccoli for the last 2 minutes. Drain. Return to the pot and mash roughly with a fork. Set aside.
Heat oil in a frying pan over medium-high heat. Add spring onion and celery and cook, stirring, for 3 minutes or until softened. Add cumin, garam masala, ground coriander, turmeric, chilli powder, dried oregano and lamb mince and cook for 5-8 minutes until mince is brown.
Add carrot, zucchini, chopped tomatoes, potato and broccoli mash and, cook, stirring for 8-10 minutes until lamb is cooked. Stir in the spinach and stir until spinach has wilted.
Transfer the meat mixture to the greased baking dish.
Scrunch each filo pastry sheet into very loose balls and place on top of the pie. Repeat with remaining filo sheets. Spray filo with olive oil and place in the oven to cook for 5-10 minutes, or until golden and flaky.
Allow to cool. You can either freeze the lamb bake in the ovenproof dish that it was cooked in or portion out and freeze in individual freezer bags or airtight containers.
Once reheated, divide the spiced lamb bake between 4 bowls.