Heat oil in soup pot or dutch oven to shimmering. Add onions and cook stirring often until onions soften, about 5 min. Add the cashews and cook, stirring, until the onions are translucent and the cashews have slightly browned, about 3 min. Stir in the garlic and cook for 30 sec. Add the squash, broth, ginger, cumin, coriander, curry powder, turmeric and stir to combine. Season to taste with salt and pepper, bring the soup to a simmer. Reduce the heat to low, cover the pot, and cook until the squash is easily pierced with knife, 20-25 min. Uncover the soup and let it cool for 15 min.