a large piping bag, a large star-shaped pastry tip
Crush 1/2 cup chopped freeze-dried strawberries to a fine powder in a blender. Set aside.
Puree the thawed frozen strawberries in the blender until very smooth. Strain into a medium saucepan and add the sugar and corn syrup. Bring to a boil over medium-high heat, stirring until the sugar is completely dissolved. Attach a candy thermometer to the pan and continue to boil until the temperature reaches 240 degrees F.
Stir together the gelatin and 1/2 cup cold water in the bowl of a stand mixer fitted with a whisk attachment. Turn the mixer to low and carefully pour the warm syrup into the gelatin. When you have added all the syrup, turn the mixer to high and beat until the mixture is very thick and holds stiff peaks, about 15 minutes. Beat in the strawberry powder. Transfer the mixture to a large piping bag fitted with a large star tip.
Put 14 of the chocolate chip cookies flat side up on a baking sheet lined with parchment paper.
Pipe the marshmallow mixture onto the cookies, about 1-inch high, while staying within the edge of the cookies. Top with the 14 remaining cookies, pressing down very lightly so that the cookies stick to the marshmallows. Let the marshmallows dry out and set for at least 2 hours.
Put 2/3 of the chopped chocolate into a medium heat-proof glass bowl. Heat in the microwave in 30-second intervals until the chocolate is melted and glossy, about 1 minute 30 seconds, stirring gently between each interval. The temperature of the melted chocolate should be between 114 and 118 degrees F.
Add a couple tablespoons of the remaining chocolate to the bowl and stir until almost melted. Continue adding the remaining chocolate, a couple tablespoons at a time, and once all of it has been incorporated, stir continuously until all the chocolate has melted and the mixture is smooth. The temperature of the tempered chocolate should be about 88 degrees F.
Working with 1 cookie sandwich at a time, dip half of it into the chocolate, using a spoon to evenly spread the chocolate onto the cookies and marshmallow. Once half of it is coated in the chocolate, use the spoon to scrape away any excess chocolate that is dripping off the cookie sandwich.
Working over a cutting board or a baking sheet, sprinkle the chocolate with some of the remaining 1 1/2 cups chopped freeze-dried strawberries. Transfer the cookie sandwich to a baking sheet lined with parchment paper.
Repeat this process with the remaining cookie sandwiches, chocolate and freeze-dried strawberries. Once the last cookie sandwich is dipped, allow the chocolate to set completely at room temperature, about 10 minutes.
Chopped freeze-dried strawberries bring out the strawberry flavor, but some other options for toppings include chopped toasted pecans, chopped milk chocolate candy bar with crisp rice (such as Nestle Crunch) and toasted coconut flakes.