Combine chickpeas, the liquid from the jar / can, lemon juice and tahini in your food processor. Blend on medium until the ingredients are somewhat combined, but still look grainy.
Scrape down the sides, add salt, garlic powder and parsley. Keep blending on the highest speed for 10 minutes or until the mixture is completely smooth.
Scrape down the sides and add more chickpea liquid or some cold water as needed to keep the consistency smooth.
With the food processor running on lowest speed, drizzle in 2 tablespoons of olive oil until incorporated. Taste and adjust seasonings, add more salt and lemon juice if needed.
To serve, spread hummus over a plate with the back of a spoon, creating little dents along the way. Drizzle with olive oil and some chopped parsley. Keep leftover parsley hummus in an airtight container in the refrigerator and eat within 4 days.
Notes
Make sure you stir tahini really well before using. If it's been standing undisturbed for a while, the oil will separate and float to the top, making the sesame paste really thick and hard. I like to stir it with a fork until it's all combined again.2 1/2 cups of chickpeas is about 400 grams or 14 ounces. If buying jarred or canned chickpeas, look for the net amount listed. The "net weight" is the weight of the chickpeas without the liquid they come in. If the can you're buying weighs a bit more, that's perfectly okay, just use the whole thing and adjust the seasonings, add a bit more parsley and you're good to go. I use the liquid from the jar along with the chickpeas. When blended, it gives the hummus a fluffier texture. If you're using home-cooked beans, use some of the cooking liquid. If you have neither, just use water.