Combine the chocolate liquor, dark chocolate, and butter and melt over a water bath. Set aside.
Combine the sugar, milk, invert sugar, and glucose syrup in a saucepan. Cook to 112°C/234°F, stirring constantly. Remove from the heat and stir in the salt.
Pour the cooked sugar mixture into a large bowl. Allow to cool, undisturbed, to 90°C/194°F.