Adapted from Julie Sahni's "Khatte Channe," Classic Indian Cooking
Heat the oil in a heavy-bottomed dutch oven or other soup pot. Add the onion and cook over medium high heat until caramelized, stirring frequently.
Add the garlic-salt mash, garam masala, cumin, turmeric, and crushed red pepper flakes. Stir and cook for a minute to bring out the flavor of the spices. Add the tomatoes and ginger and stir while cooking a couple minutes.
Add the tamarind-water, drained chickpeas, and 1 cup broth/water. Bring to a boil then reduce heat to maintain a gentle simmer, cover with a slight space to vent steam, and cook for 15 minutes or up to 1 hour—the flavors develop as cooking time extends. Take a look at how things are progressing and give it a stir now and then.
Serve with basmati rice and cucumber raita (see note).