Place chickpeas in a medium pot and cover with water by 1″. Bring to a boil over high heat, then reduce heat to medium-low and simmer, undisturbed, until chickpeas start falling apart, about 20 minutes. Reserve 1 cup cooking liquid, then drain chickpeas.
Transfer chickpeas to a food processor. Add garlic, lemon juice, tahini, salt, and 2 Tbsp. reserved cooking liquid and process for a full 5 minutes (set a timer for this) until creamy and smooth. If at any point the hummus appears dry or very thick, add cooking liquid 1 Tbsp. at a time. With the motor running, stream in oil and process just until combined. Transfer to a medium bowl and drizzle with more oil.
Do Ahead: Hummus can be made 5 days ahead. Let cool, then cover and chill.