Soak chickpeas in water for about 2 hours, rubbing occasionally while soaking to help remove the outer skin. Discard any skins that come loose. Drain chickpeas.
Combine chickpeas, water, and vegetable broth in a multi-functional pressure cooker (such as Instant Pot®). Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 20 minutes. Allow 10 to 15 minutes for pressure to build.
Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove the lid.
Strain chickpeas, reserving 3/4 cup of cooking liquid. Set aside 1/4 cup cooked chickpeas for garnish and transfer remaining chickpeas into the bowl of a food processor fitted with a blade. Add 2 tablespoons olive oil, tahini, lemon juice, and garlic. Blend until smooth, about 3 minutes, scraping down the sides. Add 1/2 cup of the reserved cooking liquid. Blend until creamy adding more liquid if necessary. Mix in 5 teaspoons harissa paste and salt.
Scrape hummus into a bowl. Drizzle remaining 1 tablespoon olive oil and 1 teaspoon harissa paste and swirl with a knife, but do not mix in completely. Sprinkle with the reserved, whole chickpeas. Serve at room temperature.