Anyway, I have to confess that I stole the idea for brandy snap ice-cream from the super awesome Gourmet Ice-Cream Company, but due to being a poor student and developing an addiction I quickly figured out how to make my own. Which I now, somewhat precociously, think is far better than theirs (theirs is still pretty awesome).
The test to tell when it's done is the traditional but somewhat vague 'coats the back of a spoon' criteria, commonly applied to custard. Basically, if the mixture is viscous enough to form a layer on the spoon, instead of running off, and if you can then run your finger (or another spoon) through it, and the edges hold the custard rather than letting it flood back over the surface, you're good. The photo on the right above shows what I mean (albeit poorly); you can (hopefully) see a strip in the middle of the spoon where there's no custard.
You can vigorously stir the mixture every so often as it freezes, if you don't have an ice-cream maker (which is about as single-use as space consuming kitchen appliances come!) - it won't be quite as creamy but it will definitely still taste good!
As well as filling 16 brandy snaps (which, incidentally, I bought, due to laziness and not being very good at shaping them) I got almost a litre of ice-cream, which I then mixed broken brandy snap bits into.
Brandy Snap Ice-cream
125ml full-fat milk
130g / 2/3 cup sugar
2 tsp ground ginger
4 egg yolks
3 Tbsp golden syrup
2-3 packets of brandy snaps (or your own homemade ones!)
Warm the milk, 125ml of the cream, sugar and ginger in a medium saucepan. Pour the remaining cream into a large bowl, set a strainer/sieve over the top, and set aside. Whisk the egg yolks in another bowl. When the milk is warm, gradually pour over the yolks, whisking constantly (this is to gradually warm the yolks and prevent them going lumpy).
Pour the egg mixture back into the saucepan, and stir constantly over a medium heat, scraping the bottom as you go, until the mixture thickens and coats the back of a spoon. Strain the mixture into the cream, then warm the golden syrup and stir it in. Chill the mixture overnight, then churn in your ice-cream maker. When thick and creamy pipe into brandy snaps, or break them into small pieces and mix through.
If you don’t have an ice cream maker, put the ice-cream in the freezer in a bowl and stir vigorously with a fork every half hour until it starts to firm up.