Perform a quick release by moving the Pressure Release to Venting. Open the pot and coarsely mash the figs with a potato masher or wooden spatula. Add the walnuts, pistachios, ghee, and cardamom and stir together. Press the Cancel button to reset the cooking program, then select the low Sauté setting and cook the halwa, stirring frequently, until it thickens to a pudding-like consistency, about 10 minutes. Press the Cancel button to turn off the Instant Pot.