Heat the oil in a large Dutch oven or stockpot. Saute the onion over medium-high heat until soft, about 5 minutes. Add the garlic and ginger, and continue to cook until fragrant, about 2 minutes.
Carefully stir in the pumpkin, stock, coconut milk, maple syrup, siracha, and salt. Bring to a boil, then turn the heat to medium-low and simmer for 15-20 minutes, until the soup has reduced and thickened slightly.
Puree with an immersion blender or in a stand blender until very smooth. Garnish with cilantro leaves or toasted coconut.