India has many snack foods. This one is a showcase for spices, which work a symphonic magic on the ground bass of the unassertive chickpea. I suggest using dried chickpeas although canned chickpeas are entirely acceptable, if a bit soft.
Soak the chickpeas overnight in 2quarts of cold water.
Drain the chickpeas over a large saucepan. Bring their soaking water to a boil with the baking soda. Simmer the chickpeas in the water for 20 minutes until just barely tender.
Meanwhile, slice the ginger piece into julienne strips. Set to soak in the lemon juice. Reserve. Peel the onion and slice it. Quarter the tomatoes. Reserve the onion slices and the tomato quarters.
Drain the chickpeas and return to the saucepan.
Tie up the black cardamoms, cinnamon, cloves, crushed ginger, and tea leaves in a small piece of cheesecloth.
Heat 3tablespoons of the oil in a small skillet and pour over the chickpeas. Toss in the pouch of spices. Stir a few times, cover, and sweat until the chickpeas are tender but not mushy, about 10 minutes. Remove from the heat, discard the spice pouch, and set the chickpeas aside.
In a large saucepan, heat the remaining 2tablespoons oil. Toss in the ajwain seeds. Stir over medium heat until the seeds crackle. Stir in the chickpea flour and stir until it gives off a noticeable aroma. Immediately stir in the pomegranate seeds, the mango powder, the cayenne, the black salt, the fenugreek leaves, the cumin, and salt to taste. Stir-fry for 2 minutes. Then add the chickpeas and Stir-fry for a few minutes until they are covered with all the ingredients and heated through.
Transfer to a serving bowl. Garnish with the ginger strips (drained), the onion slices, the tomato quarters, and the green chiles.