PREHEAT oven to 225F and line 2 baking sheets with parchment paper.
IN the bowl of an electric mixer, beat egg whites on low-medium speed with the whisk attachment until the whites become foamy. Add the cream of tartar and turn speed up to medium, beating until just fluffy. Add the sugar gradually, so it incorporates into the whites slowly without collapsing them. Once all the sugar has been added, add the vanilla and increase the speed to high, whisking until the meringue is firm and glossy, about 5 to 7 minutes.
PLACE meringue mixture into a decorating bag with a medium-size nozzle attached. Pip 24 bite-size "kiss"-shape meringues onto the trays and place in the oven. Bake for 1 hour undisturbed then turn off heat and leave in the oven overnight to really dry out.
MELT chocolate over a double-boiler or in the microwave on medium power for 30 second. Holding each meringue by the peak dip the bases in chocolate so the bottom half of the meringue is coated. Let any excess chocolate drop of before placing on the cookie sheet lined with wax paper. Allow to set at room temperature - do not put in the fridge. Once set, store in an airtight container.