Pierce the eggplants in a few places with a fork, so steam has somewhere to go when you cook them.
For a smoky flavor that will add depth to the finished dish, grill the eggplants on a very hot, oiled grill pan (or barbecue) until the skins are wrinkled and black, and the eggplants shriveled and soft; turning often. (If you prefer, roast the eggplants in a preheated 400 degree F oven for 30 minutes.)
When the eggplants are cool enough to handle, split them open and scoop out the flesh, discarding the skin and as many seeds as possible.
In a food processor, combine the garlic, tahini, lemon juice and parsley; puree until smooth. Add the eggplant flesh; season with cumin, salt, and pepper; pulse several times to make a thick, coarse puree. Pour in the oil and pulse again to incorporate. Taste and adjust seasoning, as needed. Pour into a serving bowl and garnish with chopped pistachios. Serve with pita wedges for dipping.