Preheat oven to 180 degrees C. Line 2 baking trays with aluminium foil.
With an electric beater, beat egg whites until peaks form. Add sugar into the egg whites 1 teaspoon at a time. Gently stir in vanilla and salt, beat until the egg white are stiff and shiny. Fold in chocolate chips.
Drop mixture by teaspoons onto the trays. Turn off the oven, place the biscuits inside the oven and leave them for a few hours or overnight. When you remember to look for them, they'll be ready to eat!