Yes, you can make your soft cookies become hard and crunchy without melting them by using a process called "over-drying." Here's how you can do it:
Preheat your oven: Preheat your oven to a low temperature, around 250°F (120°C).
Line a baking sheet: Line a baking sheet with parchment paper or a silicone baking mat.
Spread the cookies: Place your soft cookies in a single layer on the prepared baking sheet. Make sure they are not touching each other.
Bake at low temperature: Place the baking sheet with the cookies in the preheated oven. Bake the cookies at the low temperature for an extended period, usually about 20-30 minutes, or until they have dried out and become hard and crunchy.
Cool completely: Once the cookies are done baking, remove them from the oven and let them cool completely on the baking sheet. As they cool, they will continue to harden.
Keep in mind that the over-drying process can take some time, so be patient. The exact baking time will depend on the size and thickness of your cookies, as well as your oven's temperature accuracy.
It's essential to monitor the cookies during the over-drying process to prevent them from burning. If you notice that they are browning too quickly, lower the oven temperature or remove them from the oven earlier.
Over-drying cookies can alter their texture significantly, so it's a good idea to try this technique on a small batch first to see if you like the results. Additionally, keep in mind that some types of cookies may work better for this method than others, so experimentation may be necessary to achieve the desired level of crunchiness.