The secret to success when making these rich, chewy meringue cookies is to make sure the melted chocolate is just warm to the touch (not hot), and to beat the egg whites with the sugar long enough for them to be stiff, smooth, and glossy. Because the end result depends on the quality of the chocolate, select a high-grade variety.
1. Preheat oven to 350°F. Line 2 baking sheets with parchment paper or silicone baking mats.
2. Melt 9 oz. (1 1/2 cups) chocolate chips in large bowl set over simmering water. Cool until just warm to touch. Stir in vanilla and salt.
3. Beat egg whites with electric mixer in separate bowl 2 minutes, or until white and foamy. Add sugar 2 Tbs. at a time, beating constantly. Continue to beat 6 to 8 minutes, or until soft peaks form and meringue is snowy white.
4. Fold meringue into melted chocolate until no white streaks remain and batter is stiff. Stir in remaining 3 oz. (1/2 cup) chocolate chips.
5. Drop cookies by heaping tablespoonfuls onto prepared baking sheets. Bake 10 minutes, or until cookies look dry. Cool on baking sheets. Store in airtight containers.