Heat the oil in a heavy saucepan over medium heat. Add the cumin seeds, bay leaf and optional cinnamon. Stir briefly until fragrant, without letting the spices burn.

Add the onion and cook for 5–7 minutes, until softened and lightly golden. Stir in the ginger-garlic paste and chilies and cook for about 1 minute.

Add the tomatoes, coriander, turmeric, chili powder, ground cumin and a little salt. Cook for 5–7 minutes, stirring, until the tomatoes soften and the mixture thickens. Add a splash of the measured liquid if it starts to catch.

Stir in the potatoes and turn them through the masala for about 2 minutes, so the seasoning coats every piece.

Add the remaining measured water or broth and bring to a gentle simmer. Cover and cook for 15–18 minutes, stirring occasionally, until the potatoes are almost tender. Continue longer if needed; add a little water if the pan becomes dry.

Stir in the peas and garam masala. Simmer for about 5 minutes, or until the peas and potatoes are tender. Uncover briefly if you want a thicker sauce.

Remove the bay leaf and cinnamon stick. Taste for salt, then stir in the cilantro and optional lemon juice. Serve warm with rice or vegan flatbread, added separately.