Vanilla mascarpone ice cream

I made this ice cream without an ice cream maker - the custard base keeps it from forming ice crystals that are too big.  Adapted from BBC Good Food.

Ingredients

3 large egg yolks
100g golden caster sugar
300ml full-fat milk
250g mascarpone
seeds ½ vanilla pod (or 2 t vanilla extract)

Instructions

1. Put the yolks and sugar into a large bowl, and beat together until pale and thick.
2. Put milk, mascarpone, and vanilla into medium saucepan and bring to the boil, stirring to combine
3. Once just boiling, take off the heat and whisk this gradually into the bowl with egg mix to make a custard.
4. Pour custard back into saucepan, and cook gently for 15 mins, stirring constantly until mix is thick enough to coat the back of a wooden spoon (approximately 65-70C). Don’t let it boil or the eggs will scramble. 
5. Freeze  custard for approx. 4 hrs in a container, stirring and breaking up the crystals every hour until thick and smooth.