Preheat the oven to 200 degrees F and line a large baking sheet with parchment paper.
Wipe the bowl of a stand mixer and whisk attachment down with white vinegar.
Add the egg whites, sugar, and salt to the bowl and whisk until fully combined.
Place over a small saucepan of simmering water, and whisk frequently until it reaches 160 degrees F (70 degrees C) or until the sugar is completely dissolved and the egg whites do not feel grainy.
Move the bowl over to the stand mixer with the whisk attachment. Whisk on medium-high speed until soft peaks form.
Add the vanilla and continue whisking until stiff peaks form.
Transfer the meringue to a piping bag with a large star piping tip (I used to Ateco 867).
Pipe the meringue into kisses on the prepared baking sheet. They will not spread, so no need to space them out too much.
Bake the meringue cookies for 1 ½ - 2 ½ hours (depending on their size) or until they are no longer sticky to the touch and can easily peel off of the baking sheet.
Turn the oven off and leave the meringue cookies inside to continue to dry out.
For the chocolate coating:
Add half of the chocolate (not finely chopped) and oil to a medium bowl, and heat in the microwave in 20 second increments until fully melted.
Stir in the finely chopped half of the chocolate until smooth.
Dip each meringue cookie in the chocolate and place on a piece of parchment paper to set.
Notes
Wipe the electric mixer down with vinegar. Be sure to wipe your bowl and whisk attachment down with white vinegar. This ensures that everything is squeaky clean and nothing will hinder the egg whites from forming stiff peaks.
Do not over whip the meringue. Whip the meringue to stiff peaks, but no more! If it's over-whipped it will become dry and lose it's silky pipeable consistency.
If in doubt continue baking the meringues. If you aren't positive if the meringue cookies are done baking, just keep them in the oven and check every 15 minutes or so. So long as they do not turn brown, they'll be okay. It's better to keep them in the oven than have sticky meringues!