Put (a) in a large pan, with the cream going in first, so it sits on the bottom of the pan.
Gently heat, stirring occasionally until the sugar is dissolved, then turn up the heat and cook, stirring more often, until it reaches a 'milky coffee' colour. Remove from heat, and let stand for five minutes. After five minutes, add (b) and stir continuosly until the chocolate and butter are melted and fully incorporated. Line a gastro tray with greaseproof paper, and if using (c) sprinkle on the bottom of the tray.
Pour the fudge mix into the tray, taking care to allow (c) to stay spread around the whole base of the tray.
Allow to cool at room temperature for at least two hours.
The fudge should be fully firm when cold.
Cut to size, and store in an airtight tin/ tub until ready to use.