Whisk yolks with 1/4 cup sugar until pale in colour.
Heat on medium-high: milk, cream and remainder of sugar in a large saucepan. Once the milk is simmering remove from heat (don't allow to boil).
Slowly whisk 1 cup of the milk into the yolks, all the while whisking then pour back into the saucepan while still whisking.
Continue heating the custard base on a medium heat until it thickens (about 5 minutes). Don't allow to boil. When the base coats the back of a spoon it is ready.
Remove from heat and pour through a strainer into a bowl. Stir in the raspberry flavouring and colour.
Transfer to an airtight container and place in fridge to cool for at least 3 hours (preferably overnight).
Add to ice cream machine and churn following manufacturers instructions.
Once churned, add to airtight container and freeze for at least 2 hours until the required hardness is achieved.
