Blitz 50g of the granola until a flour-like texture has formed. Add this to a bowl with the softened butter, vanilla bean paste and honey. Lightly cream until just combined.
Using clean hands, roll the cookie dough mix into balls about the size of a pingpong ball; you should get about 18. Chill in the fridge for at least 30 minutes.
Pre-heat the oven to 180°C/fan 160°C/gas mark 4. Place the cookie dough balls onto a baking tray lined with parchment paper. Press each ball down to give a rounded shape – these cookies wont spread much, so it helps to shape them at this stage. Bake cookies in 2-3 batches in the middle of the oven for 12-16 minutes.
Whilst the cookies are baking, prepare the icing. Sift the icing sugar into a bowl then carefully pour in about 2 tbsp of the kombucha. You'll want a thick pourable consistency. Add up to another tablespoon if it needs to be a little thinner.
Check the cookies at the 12 minute point. When they're lightly golden around the edges, with a slight give in the middle, they're done. Once the cookies are cool, drizzle over the icing in a zigzag pattern freehand or using an icing bag.