Mix cookie mix with margarine in a bowl fitted with a flat beater for 3-5 minutes on medium speed until a crumble forms.
Then add water and mix on low speed until the cookie dough forms.
Divide into 50g portions and bake at 200°C in a deck oven or 170°C in a fan oven for approximately 10-12 minutes.
Blend the mincemeat with some water into a smooth paste, and transfer to a saucepan. Cook over medium heat, stirring occasionally, until the water is cooked out, and the mixture is thickened and caramelised. Cool this mixture down to room temperature.
Beat the vegan butter for 2-5 minutes until light and pale. Add in the mincemeat mixture and beat until combined.
Finally, add in the icing sugar, and beat for another few minutes until fluffy. Transfer to a piping bag and pipe a fair amount between two cookies. If you’d like, sprinkle with some icing sugar to finish.