Heat your oven to 180°C/Fan 160°C/Gas 4. Break the broccoli into small florets. Chop the stalks into 1cm-wide chunks. Pop them in a roasting tin. Add 2 tsp olive oil. Season with a pinch of salt and pepper. Toss to mix. Roast for 30 mins till a little charred. If they’re ready before the daal is finished, turn the oven off and move them to the bottom shelf to keep warm.
While the broccoli roasts, tip the lentils into a bowl. Cover with cold water. Set aside to soak.
Put a pan on a medium heat and add 1 tsp coriander seeds. Toast for 1-2 mins till they smell aromatic and pop. Tip into a mortar and grind with a pestle (or use a bowl and grind with the end of a rolling pin or the bottom of a jam jar). Set aside.
Peel and finely chop the onion. Put the pan back on a low heat. Add the onion with 2 tbsp water. Season with a little salt and pepper. Gently cook and stir for 3-4 mins to start to soften the onion.
While the onion cooks, peel and crush or grate the garlic. Finely chop the tomatoes.
Stir the garlic and tomatoes into the onion. Add the toasted coriander seeds, 1 tsp cumin, 1 tsp black mustard seeds and 2 tsp garam masala. Drop in the vegetable stock cube.
Drain the lentils and add them to the pan. Pour in 650ml boiling water. Cover, turn the heat up and bring to the boil. When the lentils are boiling, turn the heat down and simmer for 25 mins, stirring now and then, till the daal has started to thicken.
Finely slice the chard stalks and shred the leaves. Stir them into the daal and simmer for 3 mins. Taste the daal and add more salt and pepper if you think it needs it. Scoop the daal into warm bowls. Top with the roast broccoli and serve.