Balsamic Hummus

Soak the chickpeas overnight, in a large bowl of cold water. In the morning (or when you're ready to cook) drain the chickpeas. In a large saucepan, combine the chickpeas and baking soda. Put over medium-high heat and cook for 3 minutes, stirring constantly. Add the 6 1/2 cups of water and bring to a boil. Cook for 20-40 minutes, or until the chickpeas can easily be mushed between your fingers. While the chickpeas are cooking, skim the foam off the pot and remove any skins that float to the surface. When the chickpeas are cooked, drain them in a strainer.
Put the chickpeas in a food processor and blend them until you have a smooth but very thick paste. Add the tahini, 2 Tbsp lemon juice, 4 cloves garlic, 4 Tbsp balsamic vinegar and 1 1/2 tsp salt. Blend again, until everything is thoroughly mixed - you'll want to stop once or twice and scrape up the tahini from the bottom corners of your food processor. Taste and add more garlic, lemon, balsamic vinegar, or salt to taste. Drizzle in 3 Tbsp of the ice water and turn on the food processor, letting it run for a few minutes now, until you've achieved a beautifully smooth paste.
Cover with plastic wrap, pressing the plastic onto the hummus to prevent a skin from forming. Let the hummus come to room temperature (about 30 minutes). You can also cover it and refrigerate it until you'd like to eat it, but remove it from the fridge 30 minutes beforehand so it can come to room temperature.