Use a food processor fitted with a metal blade to combine chickpeas, garlic (optional) and spinach. Pulse until chickpeas and spinach are finely chopped, scraping the sides of the bowl, if necessary. Add cheese, lemon juice and pepper and pulse until blended. Gradually add enough water to thin the dip to desired consistency. Transfer to a serving bowl.
For a warm dip, transfer to a small baking dish. Bake in preheated 350°F (180°C) oven or toaster oven for about 20 minutes or until warmed through. To microwave, transfer to a microwave-safe bowl and microwave on Medium (50%) power for 2 to 3 minutes, stirring once, or until warmed through.
Serve with veggies and breads for dipping.