Tip the lentils into a bowl, cover with cold water and set aside to soak. Peel and finely chop the onion. Dice the tomatoes. Peel and grate the garlic and ginger. Halve the chilli, scoop out the seeds and white pith, then finely chop the chilli.
Put a medium pan on a medium-low heat and warm it for 1 min. Add the chopped onion and tomatoes with 2 tbsp water and a pinch of salt. Steam fry, stirring now and then, for 5 mins till the veg have started to brown and soften.
While the veg fry, crumble the stock cube and coconut cream into a heatproof jug. Pour in 500ml boiling water and stir to dissolve the stock cube and coconut cream
Stir the garlic, ginger and chilli into the veg. Stir in 2 tbsp Bombay spice mix. Drain the lentils and tip them into the pan. Mix well, then pour in the stock. Pop a lid on the pan, turn the heat up and bring to the boil. When it’s boiling, turn the heat down to low and simmer for 20 mins till the lentils are tender. Stir every few mins to stop them sticking.
While the lentils simmer, trim the bottoms off the Brussels sprouts and pull off any torn leaves. Halve them.
Warm a frying pan over a medium-high heat for 1 min, then add ½ tbsp oil and the sprouts. Fry for 5 mins, stirring often, till the Brussels sprouts start to brown. Lift them out of the pan and pop them on a plate.
Add 1 tsp each black mustard and cumin seeds and the curry leaves to the frying pan. Sizzle for 1 min till the seeds start to pop. Tip the sprouts back into the pan and add 2 tbsp water. Steam fry for 3-4 mins to just warm the sprouts through and mingle the flavours.
Add 1 tsp each black mustard and cumin seeds and the curry leaves to the frying pan. Sizzle for 1 min till the seeds start to pop. Tip the sprouts back into the pan and add 2 tbsp water. Steam-fry for 3-4 mins to just warm the sprouts through and mingle the flavours.
Taste the lentils and add a pinch more salt if you think they need it. Spoon them into 2 warm bowls. Top with the Brussels sprouts and the fried spices. Serve straight away.