Stir together the chickpeas, baking soda, and about 6 cups of water in a large saucepan over medium-high heat and bring to a boil.
Place a lid on the pan and reduce the heat to medium-low then simmer the chickpeas over medium-low until the chickpeas are very tender, about 1 hour.
Drain the chickpeas and place into a food processor along with the pumpkin puree, lemon juice, five-spice powder, 3/4 tsp salt, 1/4 tsp black pepper, and the ice cube then blend until smooth.
Transfer the hummus to a serving bowl then stir in the olive oil.
Taste the hummus and season with additional salt & pepper if needed.