Preheat the oven to 400 degrees.
Using a fork, poke a few holes into the eggplant and place on a baking sheet (optional: line the sheet with foil or parchment paper).
Bake the whole eggplant for one hour.
While the eggplant is cooking, grate the onion and place in a small colander over a bowl or in the sink. Let strain for 20 minutes or until you are ready to make the dip.
Remove the eggplant from the oven and let cool for 20-30 minutes.
Peel off the skin and move the flesh of the eggplant into a colander and let strain for an additional 20-30 minutes (you might be tempted to skip this step, but straining will remove a couple tablespoons of liquid). Discard the skin.
Place the eggplant in a medium-size bowl and add in the onion, crushed garlic, some salt and pepper to taste, 1 tablespoon of red wine vinegar, and the parsley. Use a spoon to stir the ingredients until just combined. Then, slowly drizzle the olive oil in while continuing to stir (start with a 1/3 of a cup, depending on the size of the eggplant. Use more oil if closer to a 2lb eggplant).
Taste and adjust with extra olive oil, vinegar, or seasoning if necessary.
Place in the refrigerator a few hours before serving to allow the flavors to meld together.