Put canned chickpeas* in a high-powered blender (or food processor) and puree for 1-2 minutes. If the puree looks dry, add about ¼ cup (60 mL) of the reserved liquid from the can.
Add the garlic, cumin (if using), lemon juice, salt, olive oil, and tahini. Blend for another 1-2 minutes until the mixture has lightened in color, looks smooth, and is of spreadable consistency.
Taste the hummus for salt and lemon balance, and alter if desired. (Hint: if it tastes a little bland, it likely needs more of both).
Refrigerate the hummus for at least one hour before serving.
To serve, spread the hummus on a small plate, forming a layer that is about 1 inch/2.5 cm thick. Smooth the surface of the hummus with the back of a spoon, making a few trenches as you do this. Drizzle a little olive oil into the trenches, sprinkle the top with the chopped parsley, halved olives, tomato slices, and cooked chickpeas. Serve with warm flatbreads and/or Romaine lettuce leaves to scoop.