Line a baking tray with parchment paper. You can dot a small amount of melted chocolate in each corner to help the paper stay in place.
Place the chocolate in a heatproof bowl and melt.
Spoon a circle of the melted chocolate onto the parchment paper then using a clean paintbrush (that has only been used for food or is brand new) drag the chocolate to the length that you want.
Repeat the process and place the chocolate in the fridge to chill.
Once the cake has been decorated with buttercream, remove your chocolate brushstroke decorations from the fridge. Using a clean paintbrush gently brush gold lustre on to some of the chocolate decorations.
Carefully peel the decorations from the parchment paper and stick to the cake in a random pattern. Serve immediately as the decorations may begin to melt.