Channa is also known as chickpeas, garbanzo beans or ceci beans. Aloo on the other hand is what we Trinidadians refer to potato. Hence the term channa and aloo. In this dish, channa and aloo are simmered in a fragrant curry sauce flavored with aromatics including cumin and fresh herbs.
Pick over chickpeas, remove any stones and debris and wash with several changes of water. Soak chickpeas in about 5 cups of water overnight. Drain.
Add 8 cups of water and chickpeas to a saucepan and bring to boil over high heat. After it comes to a vigorous boil, reduce heat to medium. Continue cooking until fork tender but not mushy, about 20-25 minutes(could take longer on your stove). Strain, reserving liquid (produces about 5 cups of liquid).
Grate or mince garlic. Mince culantro. Peel, wash and cut potatoes in quarters lengthwise, wash and roughly chop scallions and thyme. [chopped thyme sprigs are inedible and could be dangerous for kids. For this reason, I usually keep thyme whole and remove whole sprigs after cooking is complete.]
Make curry paste. Mix curry, half of garlic(6 cloves), minced culantro (bandhania) and 1/2 cup water in a small bowl.
To cook:
Pour oil into a large heavy bottomed pot over high heat, heat. When hot, add methi, cook until it darkens. Add the onion and hot pepper, cook for 3 minutes. Add remainder of garlic and cook until the edges of the onion become golden brown.
Add curry paste and cook until it darkens, becomes grainy and fragrant and separates from oil, about 3-5 minutes. At this point you can rinse the "curry paste" bowl with a little water{1 tablespoon} and add to pot.
Add potatoes and cook for about 3 minutes, stirring constantly.
Add chickpeas, scallion, thyme, remainder of minced culantro and salt. Cook about 3-5 minutes, stirring occasionally to prevent chickpeas and potatoes from sticking.
Add reserved liquid and enough water to cover the chickpeas and potatoes, about 5-6 cups. Stir, scraping up the spices at the bottom of the pot.
Bring to a boil. Reduce heat to low, cover and cook, [stirring every 8 minutes and cutting potatoes in half using spoon], until potatoes are tender and sauce thickens (but not totally evaporated), about 40-60 minutes. [At the end of cooking, I mash about 4 pieces of potato with the back of the spoon to allow the sauce to thicken more rapidly]. If the chickpeas are not tender enough for your liking, continue to add two cups of water, in increments, until it's your desired texture. Some like it more firm than others. It helps to stir the pot repeatedly for about 5 minutes to bring it to the right consistency.
Remove cover, stir in cumin and chopped culantro and cook for an additional 5 minutes until sauce thickens but is not totally evaporated.
Rest for 10-15 minutes before serving to allow sauce to thicken further.