No Bake S'mores Cake

Bahan-bahan (12 porsi)

• three 4-ounce bars (339g) semi-sweet or milk chocolate, finely chopped*
• 1 and 1/2 cups (360ml) heavy cream
• 6 egg whites, at room temperature
• 1 and 1/2 cups (300g) granulated sugar
• 3/4 teaspoon cream of tartar
• 1 teaspoon pure vanilla extract
• 30 -36 full-sheet graham crackers (a little over 1 standard box)