Mix plain flour, self-raising flour, and butter with warm water to form an elastic dough.
Roll the dough into 12 circles and cut each into half to make 24 pieces.
Fry chopped onions and panch phoran in oil until the onions are golden-brown.
Add spinach and chilli, season with salt, and cook until the spinach has wilted.
Stir in the cheese after removing the mixture from the heat.
Place a teaspoon of filling in each dough semi-circle and fold into triangles.
Heat oil in a deep pan and fry samosas in batches for 5 minutes until crisp.
Drain the samosas on kitchen paper and serve.