Preheat the oven to 375F. Clean and prick the sweet potatoes a few times with a fork, and line two baking sheets with parchment or foil. Place the potatoes on one sheet. Toss all of the tandoori chickpea ingredients together in a mixing bowl and place them on the other sheet. Transfer both sheets to the oven. Roast the chickpeas for about 30-35 minutes, stirring halfway through. Roast the sweet potatoes for 40-45 minutes, or until tender when pricked with a fork. Allow both sheets to cool.
While the ingredients roast, whisk together all of the ingredients for the tahini lime drizzle. Then, bring a small pot of water to boil and gently boil or steam, then drain, the leafy greens.
When the potatoes have cooled a bit, cut them in half and very gently scoop out the flesh (careful not to pierce the skins when you do this). Transfer all of the flesh to a mixing bowl and mash roughly with the tahini or nut butter, plant milk, salt, and red pepper flakes. Fold in the steamed leafy greens.
Transfer the potato skins to a serving platter. Scoop the mashed potato mixture back into the skins. Top them all evenly with the roasted chickpeas. Drizzle the whole dish generously with the tahini sauce and then sprinkle it with chopped cilantro, if desired. Serve.