Tip the lentils into a bowl and cover with cold water. Set aside to soak. Heat your oven to 200°C/ Fan 180°C/Gas 6. Pour 1 tbsp oil into a roasting tin and slide into the oven to heat.
Peel the potatoes and chop them into small chunks around 3cm across. Tip them into a bowl. Measure out ½ tsp each of the coriander, cumin and fennel seeds and add to the bowl with 1 tsp garam masala and some seasoning.
Toss the potatoes and spices together. Tip into the roasting tin, making sure they're well spread out. Roast for 20 mins. While the potatoes roast, break the broccoli into small florets. Add to the tin after 20 mins and roast for 15-20 mins more.
While the potatoes roast, peel and finely chop the onion. Warm a pan over a low heat for 1 min. Add ½ tbsp oil and the onion. Season with a little salt and pepper. Cover and sweat for 5 mins.
While the onion cooks, peel and grate the garlic and ginger. Halve the chilli. For less heat, flick out the seeds and white bits. Finely chop it.
Drain the lentils and add to the onion. Stir in the garlic, ginger and chilli. Add 1 tsp each of the cumin, coriander and fennel seeds along with 1 tsp of the garam masala. Tip in 6 curry leaves. Add 1 cinnamon stick and 1 bay leaf.
Pour in 500ml boiling water. Cover and turn up the heat. Bring to the boil, then turn the heat down to medium and simmer the lentils for 15 mins till they’re soft and smell aromatic. Fish out the cinnamon stick and bay leaf. Ladle the lentils into warm bowls. Top with the roast potatoes and broccoli to serve.