Drain and rinse the chickpeas, then transfer them to a large mixing bowl.
Cut the ripe avocado in half, remove the pit, and scoop the flesh into the bowl with the chickpeas.
Mash the chickpeas and avocado together with a fork or potato masher until mostly smooth but with some chunky texture still visible.
Sprinkle in the finely chopped red onion, and drizzle with lemon juice to brighten the flavors. Mix well.
In a small bowl, whisk together tahini, minced garlic, and a pinch of salt and pepper until smooth and creamy.
Pour the tahini dressing over the chickpea mixture and gently fold everything together until well combined.
Taste and adjust seasoning with more salt, pepper, or lemon juice as desired. Add chopped herbs or vegetables if using.
Serve immediately for the best freshness, or refrigerate for up to a few hours to let flavors meld. The salad should be creamy with a slight crunch from the onion.
