Ottolenghi's Spiced Lentils with Cucumber Yogurt

Reprinted from The Guardian with a few notations:

200g split red lentils (available from Indian or Persian markets)
1 bunch fresh coriander (cilantro, mi amigos Americanos)
1 small onion, peeled
40g ginger, peeled
3 cloves garlic, peeled
1 mild green chili (jalapeno, see footnote*)
1½ tsp black mustard seeds (available at Indian or Persian markets)
4 tbsp sunflower oil
1½ tsp ground coriander
1 tsp ground cumin
½ tsp ground turmeric
½ tsp paprika
10 curry leaves (available at Indian or Thai markets, but grated zest of lime can be substituted in a pinch)
300g ripe tomatoes, peeled and chopped (better than tinned)
2 tsp caster sugar
½ tsp fenugreek (optional)
1 pinch asafoetida (optional) (very hard to find)
Salt
150g Greek yogurt
75g finely diced cucumber
1½ tbsp olive oil
70g unsalted butter
1½ tbsp lime juice

Wash the lentils in plenty of water, drain and soak in 350ml of fresh water for 30 minutes. Cut the coriander bunch somewhere around its centre to get a leafy top half and a stem/root bottom half. Roughly chop the leaves. Put the stem half in the bowl of a food processor, add the onion, ginger, garlic and chili - all roughly broken - and pulse a few times to chop up without turning into a paste.

Put the mustard seeds in a heavy-based pot and place over medium heat. When they begin to pop, add the onion mix and sunflower oil, stir and cook on low heat for 10 minutes. Add the spices and curry leaves, and continue cooking and stirring for five minutes longer. Now add the lentils and their soaking water, the tomatoes, sugar, fenugreek, asafoetida and a pinch of salt. Cover and simmer for about 30 minutes, until the lentils are fully cooked.

Before serving, whisk together the yogurt, cucumber, oil and some salt. Stir into the lentils the butter, lime juice and chopped coriander leaves, taste and season generously with salt. Divide into bowls, spoon yogurt on top and garnish with coriander.

** a note about chilis -- I use jalapenos when asked for a mild chili but although I love them I am very sensitive when I clean them and they always get stuck in my throat. Probably very good for the respiratory system. Last time I tied a tea towel around my face so I looked a bit like Clint Eastwood, and it still made me cough (which leads me to believe that those surgical masks being used to counteract swine flu may be ineffectual too). If you're a fair English rose like me, do also use rubber gloves when cleaning chilis, because even after washing your hands, any piece of skin you touch will itch like mad.