Peel the potatoes, cut them in half, and boil in vegetable stock until tender. Drain the potatoes and cut them into bite-size pieces.
Heat a little vegetable oil in a frying pan and gently fry the garlic, chilli, cumin, garam masala, onion powder, turmeric, and coriander powder until fragrant.
Add the chopped tomatoes, season with salt, and cook until they release their juices and soften.
Sprinkle the fenugreek leaves over the tomatoes and cook for another minute.
Mix the cornflour with a small splash of cold water to form a paste, then stir it into the tomato mixture. Pour in the vegetable stock, bring to the boil, and then reduce the heat to simmer until the sauce thickens slightly.
Add the spinach and stir until just wilted, about 1–2 minutes.
Gently mix the potatoes into the spiced spinach and tomato sauce (reheat the sauce slightly if needed). Cover and let it sit for 10 minutes so the potatoes can absorb the flavours.
Serve warm, or refrigerate and enjoy chilled as a spiced potato salad.