1 (4-ounce) package semisweet chocolate baking bar, finely chopped (we tested with Ghirardelli)
How to Make It
Beat egg whites, vinegar, and salt at high speed with an electric mixer until foamy; gradually add sugar, beating until stiff peaks form and sugar dissolves. Fold in chocolate. Drop by heaping teaspoonfuls onto parchment paper-lined baking sheets. Bake at 250° for 35 minutes. Transfer to wire racks to cool completely.