Put the cream and milk in a pan then bring to a simmer. Whisk the egg yolks, sugar and Horlicks in a bowl then pour over the hot milk, whisking until everything is combined. Pour the mix back into a clean pan then cook over a low heat until the custard thickens enough to coat the back of a spoon. Strain through a sieve into a bowl, cover the surface with clingfilm to stop a skin forming and put in the fridge until chilled. Pour into an ice cream maker and churn until frozen.