Cook's note: You can use sour cream if you don't have or like Greek yogurt.
Preheat oven to 400 degrees.
Slice the eggplant in half, lengthwise. Place on baking sheet lined with foil, and spray with cooking spray. Roast for 35 minutes.
Once cooled slightly, scoop out the inside of the eggplant and place into a blender or food processor. Add garlic (2 cloves if you really like the garlic flavor!) and process until smooth. Add the yogurt, tahini and lemon juice and blend until smooth. Taste, and add desired amount of salt and pepper.
Place in a bowl and top with parsley and a drizzle of olive oil. Serve with warm pita or pita chips.