Strain garlic mixture through a fine-mesh sieve into a small bowl, pressing on solids to release as much liquid as possible. Return liquid to food processor; discard solids. Add tahini and pulse to combine. With motor running, add 1/4 cup ice water by the tablespoon and process (it may seize up at first) until mixture is very smooth, pale and thick. Add chickpeas and cumin and puree for several minutes until the hummus is smooth, pale and thick. Then puree some more! Taste and adjust the seasoning with salt, lemon juice and cumin if you like.