Step 1: Preheat oven to 200°F (95°C). Line two large baking sheets with parchment paper. If using, lightly crush the freeze-dried raspberries into small pieces; set aside.
Step 2: In a very clean, large glass or metal mixing bowl, beat egg whites with an electric mixer on medium speed until foamy. Add cream of tartar; beat on high speed until soft peaks form.
Step 3: Gradually add sugar, 1 tablespoon at a time, beating on high speed until stiff, glossy peaks form and the sugar is completely dissolved. The mixture should be very thick and hold its shape.
Step 4: Gently fold in vanilla extract and red liquid food color (if using). Then, very carefully fold in the crushed freeze-dried raspberries and miniature semisweet chocolate chips, taking care not to deflate the meringue.
Step 5: Transfer the meringue mixture to a large piping bag fitted with a star tip (or use a zip-top bag with a corner snipped off, or simply use two spoons). Pipe or drop 1-inch mounds onto the prepared baking sheets, spacing them about 1 inch apart.
Step 6: Bake for 1 hour 15 minutes to 1 hour 30 minutes, or until the meringues are firm and easily lift off the parchment paper. They should be dry to the touch.
Step 7: Turn off the oven and leave the meringues inside with the oven door slightly ajar for at least 30 minutes, or until completely cool. This helps prevent cracking and ensures they are perfectly crisp.
Step 8: Once meringues are cool, prepare the dark chocolate dip. In a microwave-safe bowl, combine the 1 1/2 cups dark chocolate chips and shortening. Microwave on 50% power in 30-second intervals, stirring after each, until smooth and melted. Alternatively, melt in a double boiler over simmering water.
Step 9: Dip the cooled meringues halfway into the melted dark chocolate, allowing excess chocolate to drip off. Place on a parchment-lined baking sheet or wire rack until the chocolate is set. This can be sped up by placing them in the refrigerator for 10-15 minutes.