Preheat the oven to 300 degrees F, and line a large baking sheet with parchment paper.
In a kettle or small saucepan, bring 1 cup of water to a boil. Place 1 cup of the pitted dates in a small bowl, and top with just enough boiling water to cover. Soak for at least 5 minutes, until very soft. Chop the remaining dates and set aside.
Drain the dates, reserving the soaking water, and place in a food processor. Add 3-4 tablespoons of the soaking liquid, and puree until creamy. Transfer to a medium bowl and combine with the tahini, salt, and cardamom, stirring until smooth (Note: tahini consistencies vary. You want the mixture to be thin enough to easily toss with the other ingredients. If it seems too thick to combine with the oats, you can add another 1-2 tablespoons of the date soaking liquid).
In a large bowl, combine the rolled oats, pistachios, and flax seed. Add the liquid mixture, and stir until the oats are wet and the mixture is thoroughly combines.
Spread into a thin layer on the prepared baking sheet, and bake for 25-30 minutes, flipping the oats once or twice midway through. The granola should be dried out and fragrant.
Allow to cool, then toss with the remaining dates. Store at room temperature in an airtight container.
I usually serve this with plain yogurt or soy milk.