Steam the potato until cooked. Preheat the oven to 180 °C. In a deep pan, dry roast the onion and garlic until translucent. Add thyme, rosemary, red chilli flakes, and spinach and sauté until the leaves wilt. Remove from heat. Add millet, cashew cheese, lemon zest, ground pepper, salt, potato and broccoli to the spinach-onion mixture, along with vegetable stock and stir until well combined. Pour the mixture into the prepared baking dish, and place in the preheated oven. Bake for 30 minutes or until set and the edges are brown. Allow it to cool slightly before slicing. Serve warm or at room temperature (it tastes good when cold too).