Mix the nutritional yeast, lemon juice, olive oil, garam masala and salt together in a large bowl to form a paste. Drain the tofu and cut it into bite sized cubes then toss them in the marinade until they are well coated. Set aside for 30 minutes to marinate. (It can be baked right away if you don't have time).
Preheat the oven to 200°C/180°fan/400°F/gas mark 6. Spread the tofu out on a baking parchment lined baking sheet and bake for 20-30 minutes, turning it over halfway through, until it is golden and crisp.
To make the sauce, defrost the frozen spinach (I just do this in the microwave) then transfer it to a food processor or blender (I don’t bother draining off the excess liquid unless it is very soupy) and pulse until it is finely chopped. Set aside.
Heat the oil in a large pan over a low heat and add the cumin seeds. Cook for a couple of minutes until they are fragrant then add the finely chopped onion. Cook gently for about 10 minutes until the onion is soft and translucent. If it starts to catch on the bottom of the pan you can add a splash of water to stop it sticking.
Add the grated ginger, crushed garlic and chopped green chillies and cook for another minute.
Add the garam masala, ground coriander, turmeric and fenugreek leaves and cook for a minute while stirring.
Stir in the coconut cream followed by the chopped spinach, some salt to taste and a squeeze of lemon juice. Bring up to a simmer and cook for about 10 minutes, stirring often. If the sauce seems too thick you can add a splash of water but I do prefer it to be on the thicker side.
Stir in the baked tofu and check the seasoning, adding more salt and lemon juice as needed, then serve.