Set a steamer basket in a large pot. Fill with enough water to come just below basket, bring to a boil. Add sweet potatoes, reduce to a simmer, cover, and cook until tender, 10 to 12 minutes.
Transfer to a food processor. Combine chickpeas, lemon juice, tahini, oil, cumin, and garlic in the food processor. Puree about 1 minute, thin with water if necessary. Season with salt and pepper and let cool.
Refrigerate hummus in an airtight container up to 1 week. Serve with pita and or crudités.