In a small skillet, warm the ground cumin and ground coriander over low heat for 1–2 minutes, stirring constantly, until aromatic. Remove from heat and set aside.

In a high-speed blender or food processor, combine the chickpeas, chickpea water, garlic, tahini, lemon juice, olive oil, harissa, salt, and the toasted spices. Process for 1–2 minutes, pausing to scrape down the sides as needed, until the mixture is completely smooth and creamy. For a thinner consistency, add additional water in 1-tablespoon increments, processing briefly after each addition.

Transfer to a serving bowl. For the optional topping, spoon additional harissa over the surface, drizzle with olive oil, and top with a few whole chickpeas. Finish with a light dusting of smoked paprika, coarsely cracked peppercorns, and coarse sea salt. Serve at room temperature or chilled.