1. Put raspberries in an ice cube tray.

2. Fill with water and put in the freezer.

3. Place about 4/5 raspberries in a strainer and crush with a spoon.

4. Pour the puree you've obtained into the glass you've chosen to make your gin.

5. Add 4 ice cubes followed by the gin and tonic water. 

6. Finish with a sprig of rosemary.