Cream together the butter and icing sugar until light and fluffy, approximately 2 minutes.
Whisk in the vanilla.
Fold in the flour and green tea leaves, direct from the tea bag, until a dough is formed.
Transfer to a piping bag with a desired tip and pipe on a non-stick baking tray without parchment paper.
Refrigerate for 5-10 minutes if too soft.
Bake at 160°C for 13-15 minutes for chewy, or for 18-20 minutes for crispy until nicely golden brown.
Let cool completely before storing in an airtight container.