Place egg whites in a medium bowl; let stand at room temperature for 30 minutes. Preheat oven to 325 degrees F. Line 2 large baking sheets with parchment paper or foil; set aside.
Add the 1/2 teaspoon vanilla and the 1/8 teaspoon cream of tartar to the egg whites. Beat with an electric mixer on medium speed until soft peaks form (tips curl). Add sugar, 1 tablespoon at a time, beating on high speed until stiff peaks form (tips stand straight).
Drop egg white mixture by rounded measuring teaspoons 1-1/2 inches apart onto the prepared baking sheets. Use the back of the teaspoon to make a small indentation in the center of each cookie. (Moisten the spoon with water between indentations.)
Bake both sheets on separate racks in the oven for 10 minutes. Turn oven off and let cookies dry in the closed oven for 40 minutes. Transfer cookies to a wire rack and let cool.*
For filling, in a small microwave-safe bowl, combine Ghirardelli(R) 60% Cacao Bittersweet Chocolate Baking Chips, whipping cream and the 1/4 teaspoon vanilla. Microwave on medium power (50 percent) for 1 minute, stirring every 30 seconds. Remove and stir. If chocolate is not melted, return to microwave and repeat heating step, stirring every 30 seconds to avoid scorching. Stir until smooth. Cool slightly. Spoon filling into cooled meringues.** If desired, sprinkle with pistachios. Enjoy immediately.