Place the licorice toffee sweets into a saucepan and stir in the milk. Bring the pan slowly up to boiling point, stirring all the time and be sure that the toffees completely melt.
This can take 5 to 10 minutes. Place to one side.
In a separate bowl, beat and mix together the egg yolks and sugar until thick.
Pour the hot milk and toffees mixture into the combined egg yolks and sugar, stirring whilst doing so. Then pour this back into the pan and heat gently; keep stirring until the custard thickens - DO NOT BRING TO THE BOIL OR IT WILL PROBABLY CURDLE. When you can see a film form over the back of your spoon it's time to remove the saucepan from the heat. Leave to cool.
When the custard base is cold stir in the cream (and the vanilla extract if you want to use it).
Transfer the whole mixture into an ice cream maker and freeze according to the manufacturer's instructions.