I started with a Chat de langue (cats tongue) biscuits recipe and improvised from there:
Chat de Langues:
100g Icing Sugar
1tsp Vanilla essence
2 Egg whites
120g Plain flour
Pre heat Oven 200 c
Blend the butter and icing sugar and vanilla essence, like a butter icing, it should be smooth and fluffy, whisk in the egg whites one at a time, then gently fold in the sifted flour. Once mixed spoon into a piping bag and pipe onto a tray with greaseproof paper (do not - like me - think that your fantastic non-stick tray will be enough to save your lovely biscuits from cementing themselves to the tray! Noooo!) yes do use greaseproof paper. Pipe them out 5cm lengths and leave enough room for them to spread out, try to keep them the same size as much as possible. Put in the oven for about 10-15 mins until lightly golden on the edges. leave to cool.
While they're cooling, melt some dark chocolate in a saucepan on a low heat, I used a 100g bar and that was plenty. Yummy.
Once the biscuits have cooled, try to pair them up, like for like, by size. It's quite hard to make them nice and consistent in shape, mine are a bit wibbly and wobbly, but I managed to find rough pairs for all of them.
Spread the melted chocolate on the underside of each biscuit - keeping an eye of the pairs as you go.
Once you've spread the chocolate on all of them, leave them to cool and wait for the chocolate to set.
While those are doing that, you can make the minty fondant filling. As this was an experiment, I didn't have exact measurements. I used a large knob of soft butter and about 5-6 heaped tablespoons of icing sugar with about 2 -3 teaspoons of mint essence (depends how minty you want it) mix together, it will look a bit like a butter icing, add a little water if needed. When the chocolate is set, spread the minty fondant on the underside of one of each biscuit pair (over the chocolate)
Stick the other biscuit pair on top like a sandwich and you're done! There is quite a lot of fiddling with this recipe, but I enjoy doing things like this on a quiet afternoon, sad? Anyway, they turned out a bit messy, I'm sure there are plenty of people who could do a much more precise, professional looking job, maybe with a bit of practice they could be better. They still taste pretty good and I don't have to go to America to get them. (maybe they do sell them in England, I don't know...?)