Melt the butter in a bowl in the microwave - it's best to do this in short, 10-15 second intervals as you want it just melted, not bubbling hot!
Add the melted butter and caster sugar to a large mixing bowl and beat with an electric whisk (or wooden spoon) until combined. Add the egg and beat again until it combines and forms a runny batter.
In a separate bowl, add the gluten free flour and baking powder and stir to mix it all together. Sift the flour mix into the butter/sugar mixture.
Bring the mixture together using a wooden spoon. Once the mixture starts to come together, add the chocolate chips, crush in the meringue nests so they're in chunks, and add the raspberries, Gently use the wooden spoon to bring the mixture together into a sticky dough - it doesn't matter if some of the raspberries get crushed as this will add a nice pink colour to your mixture!
Once it's completely mixed together (and there is no loose flour left in the bowl) wrap the dough in clingfilm and refrigerate for at least an hour.
Once the hour is nearly up, preheat the oven to 180'C / Fan 170'C / Gas Mark 4. Line two baking trays with baking paper. Take the cookie dough from the fridge and roll it into balls around the size of a golf ball. Flatten the balls onto the baking tray, making sure there is around 3cm between them in case of any spreading.
Bake the cookies in the oven for 15-18 minutes. Once baked, carefully remove the cookies from the oven and allow them to cool on the tray for 15-20 minutes before transferring to a baking tray to cool completely.
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Notes
The cookies will be very soft still when they come out of the oven so they MUST cool before you try to move them! Can be eaten warm or cold - will keep for around 5 days in an airtight container.
You can also freeze the cookie dough or baked cookies.