Pour your cream into a small saucepan and set over a medium heat until gently steaming and hot to the touch.
Add the chocolate and salt to the hot cream and allow to stand for 1 minute.
Stir the mixture until smooth, and set aside to cool and thicken slightly at room temperature while you make your biscuits.
For the biscuits:
In a large bowl, beat together the butter and sugar until pale and fluffy.
Add the egg and mix until evenly combined.
Add the flour and nutmeg and stir gently until combined and the mixture forms a stiff dough.
Tip the dough out onto a generously floured surface and knead softly for a few seconds until it is smooth all over.
Roll out the dough to about ½ a centimetre (or ¼ inch) in thickness.
Use a round biscuit cutter to stamp out as many rounds as you can from the sheet of dough. Carefully transfer the biscuit rounds to a greaseproof paper lined baking tray, you may need 2-3 trays in total.
Re-roll the scraps of dough to repeat until you have used as much of it as you can.
Use a small star-shaped cutter to stamp out star shapes from the centre half of the biscuit rounds, leaving the remaining half untouched.
Place your tray(s) of dough circles into the freezer for 20 minutes (if you can’t use a freezer, refrigerating for 45 minutes should do the job), meanwhile preheat your oven – 180 C / 160 C fan / 350 F / gas mark 4.
Once the biscuit rounds have chilled, bake them in the preheated oven for 9-10 minutes for soft and crumbly biscuits. If you prefer a crisper biscuit, bake for an extra 2-3 minutes.
Allow the biscuits to cool completely on their trays.
When cooled to room temperature, spread your slightly thickened ganache onto the full biscuit rounds before sandwiching them with the star-stamped biscuit rounds.