Rinse the lentils in a fine-mesh sieve and pick out any debris. Place the lentils and broth (or water) in a medium saucepan over high heat and bring to a boil.

Reduce the heat to medium-low and simmer, uncovered and stirring occasionally, until the lentils are tender but not mushy, about 30 minutes. Add a splash of water if the pan starts to look dry.

Set a colander over a bowl and drain the lentils, saving about ¼ cup of the cooking liquid. Return the lentils to the saucepan or spread them on a plate and let them cool completely, about 20 minutes.

Place the cooled lentils, garlic, olive oil, tahini, lemon juice, cumin (if using) and a pinch of salt in the bowl of a food processor fitted with the S-blade. Process for 2 to 3 minutes until smooth, stopping to scrape down the sides of the bowl as needed.

Taste and add more salt or lemon juice if needed. If the hummus is too thick, add the reserved cooking liquid (or water) 1 tablespoon at a time and process again.

Transfer the hummus to a serving bowl and swirl the top with the back of a spoon. Drizzle with olive oil, sprinkle with parsley, and serve with pita wedges, crackers or raw veggies for dipping.