Trim and wash the spinach but don't dry it. Chop roughly. Cut the tofu in two and wrap in paper towels then sandwich between two plates to express some of the water.
Heat the butter in a non-stick frypan. Add the ginger, garlic and chillies and cook, stirring, until the garlic starts to colour.
Stir in the garum masala and a pinch of salt and cook, stirring, about 30 seconds. Add the spinach and cook until it wilts, then add yoghurt and one cup of the cream. Pick out the chillies and discard.
Cook the spinach mixture over medium heat until the liquid has mostly boiled off. Cut the tofu into 2cm cubes and gently stir it in. Add the remaining cream and cook another minute, then test for seasoning and serve.