Beat egg whites at high speed with an electric mixer until foamy.
Add sugar, 1 tablespoon at a time, beating until stiff peaks form.
Drop by 1/4 cupfuls onto parchment paper-lined baking sheets.
Bake at 250° for 30 minutes. Turn oven off. Let meringues stand in oven with door closed 30 minutes.
Spread a thin layer of chocolate on flat sides of meringues. Let stand on wax paper 2 hours.