PREHEAT OVEN TO 350º
TOAST NUTS FOR 10 MINUTES. TURN PAN ONCE DURING THE TOASTING.
CHOP NUTS COARSELY BY HAND OR IN A FOOD PROCESSOR.
REDUCE OVEN TO 250º
PLACE THREE RACKS IN THE OVEN.
BEAT EGG WHITES WITH SALT AND VINEGAR UNTIL STIFF BUT NOT DRY. GRADUALLY ADD SUGAR UNTIL MERINGUE FORMS STIFF PEAKS. GRADUALLY ADD VANILLA.
FOLD IN THE CHOCOLATE AND NUTS WITH A RUBBER SPATULA.
USING A SMALL PIECE OF WAXED PAPER, SPREAD A PAT OF BUTTER ON EDGES OF THREE COOKIE SHEETS. PRESS A SHEET OF PARCHMENT PAPER ON EACH COOKIE SHEET.
USING TWO TEASPOONS SCOOP ABOUT 1 TBSP OF MERINGUE ON THE COOKIE SHEETS, SPACING THEM AN INCH APART.
BAKE MERINGUES 45 MINUTES OR UNTIL FIRM. HALFWAY THROUGH THE BAKING, ROTATE COOKIE SHEETS AND SWITCH POSITION OF THE SHEETS ON THE RACKS.
PLACE SHEETS ON COOLING RACKS AND ALLOW TO COOKIES TO COOL ON THE PARCHMENT PAPER.
MAKES ABOUT 40 COOKIES.