Tip the dried red lentils into a bowl. Pour over enough cold water to cover them and set aside to soak for 10 mins.

While the lentils soak, peel and finely chop the onion. Warm a large pan on a medium-low heat for 2 mins, then add 1 tsp oil and the onion. Season with a pinch of salt. Fry, stirring often, for 8 mins till the onion starts to soften and pick up some colour. If the pan seems too dry, add a splash of water and turn down the heat.

While the onion fries, dice the tomatoes. Peel and grate the garlic and ginger. Halve the chilli, scrape out the seeds and white pith (or leave them in for more heat), and finely dice the chilli. Finely chop the coriander stalks (set the leaves aside for later). Stir the tomatoes into the onion and cook, stirring often, for 5 mins till the tomatoes are pulpy.

While the tomatoes cook, scrub the potatoes (no need to peel them) and slice them into 1cm-thick rounds. Drain the lentils. Fill and boil your kettle.

Stir the garlic, ginger, chilli and coriander stalks into the veg, with 1 tbsp Bombay spice blend. Cook and stir for 2 mins till the pan is aromatic.

Tip the potatoes and lentils into the pan. Stir to mix, then pour in 700ml boiling water. Stir to mix, cover and bring to the boil. When boiling, turn the heat down and simmer for 15-20 mins till the potatoes and lentils are tender. If the pan dries out too quickly, add an extra 100-200ml water.

Stir the baby leaf spinach into the pan. Simmer without the lid for 1-2 mins till the spinach wilts.

Taste the curry and add a pinch more salt if you think it needs it. Ladle into 2 warm bowls and serve straight away.