Dieters will appreciate these low-calorie cookies so be sure to include a few on your holiday cookie tray. Mini chocolate chips boost the flavor without breaking the calorie budget.
Heat oven to 250°F. Line 2 large baking sheets with nonstick foil. Stir together vanilla and instant coffee in a small bowl. Set aside.
Beat egg whites and cream of tartar in large bowl on medium speed until frothy. Increase speed to medium-high; add sugar, 1 tablespoon at a time, and beat until stiff, glossy peaks form and whites have tripled in volume, about 5 minutes.
Sift cocoa powder over beaten egg- white mixture. Carefully fold in cocoa powder until evenly distributed. Fold in vanilla-coffee mixture and mini chocolate chips. Transfer egg-white mixture to a large resealable plastic bag. Snip off a large corner and pipe meringue by heaping tablespoonfuls onto prepared baking sheets. Bake at 250°F for 1 hour, leaving oven door closed the entire time.
Turn off oven; tilt oven door open. Let meringues stand in oven for 30 minutes.
Remove meringues from oven. With thin metal spatula, carefully lift cookies off baking sheets.