Place the squash, cauliflower and ginger in a large steamer basket over a saucepan of simmering water and season with salt. Cover and steam until the vegetables are tender, about 25 minutes. Add the snow peas, remove the pan from the heat and keep covered until the peas are crisp-tender, about 5 minutes.
Meanwhile, toast the coriander seeds in a skillet over medium-low heat until fragrant, about 1 minute. Add the sesame oil and increase the heat to medium-high. Add the chickpeas and cook until crisp, about 5 minutes. Add the butter and scallions; remove from the heat.
Divide the vegetables among plates, over rice if desired. Spoon the chickpea mixture on top and garnish with the mint and sesame seeds.