How to make your own ice-cream
Much like making your own bread, homemade ice cream depends on few ingredients - milk and/or cream, eggs, sugar and flavouring - and a bit of know-how. Don't be intimidated by the prospect of making your own vanilla or chocolate ice cream - you won't even need any elaborate contraptions to churn or freeze it, as I'll explain below.
But why would you go to the trouble of even making your own ice cream when there are so many available at supermarkets? For the same reason you'd make your own bread, yogurt, or muesli: there is a tremendous satisfaction to be gained from creating something with a smattering of ingredients, using your own fair hands. The added benefit of course is you'll know exactly what goes in your mouth, something that can't be said of commercial ice cream. Plus ice cream-making is fun, so get your mates round and start experimenting.
Ice cream, in fact, was the reason I applied to work as a stagière at the legendary Fat Duck. Seriously, seeing Heston Blumenthal enthuse about ice cream and reading his observations about how to perfect its technique was an inspiration to learn about the science of ice cream. Plus, of course, I love eating the stuff.
The peculiarity of ice cream lies in its liminal nature - neither liquid nor food, but instead a semi-solid foam frozen to just the right level of coolness so that it refreshes without losing its taste or texture. Commercial ice creams are generally full of stablisers, emulsifiers, artificial colours and flavourings, not to mention any number of weird-sounding additives which you don't need to make your own ice cream.
There are a few rules to bear in mind, as corralled from my three sources on ice cream: Heston Blumenthal's 'Big Fat Duck Cookbook', Harold McGee's 'McGee on Food and Cooking' and Peter Barham's 'The Science of Cooking.' The first step is to make a basic mixture and in most cases this will be a cooked custard consisting of egg yolks, milk and/or cream, sugar and some flavouring such as vanilla, coffee or chocolate.
According to food scientist Harold McGee, cooking your ice cream custard base will improve both texture and minimise the size of ice crystals in the end result. Minimising the size of ice crystals in ice cream is key, hence the beating of your mixture while it's freezing. In a nutshell, the various ingredients and your technique will have an effect on the molecular structures in your ice cream - too much sugar will make the ice cream 'chewy' and affect its freezing point, and too little will result in crunchy ice. Different sugars have different effects so watch out if you're thinking of substituting table sugar (sucrose) with fruit sugar (fructose) as this will have a marked effect on your ice cream. Too much milk fat can result in buttery ice cream, and impair flavour-release so follow the recipe and you'll have, in Heston's words, an ice cream which is clean-tasting and has a quick-flavour release, with a refreshing character.
Once you've made the custard base, ideally you should subject it to what McGee calls 'quiescent cooling' before churning - this will crystallise the fat and improve the ice cream's consistency. Start at least 8 hours before you want to freeze the ice cream and refrigerate the custard base between 8 and 24 hours for maximum 'maturation'. This may seem time-consuming but all you have to do is plan ahead and once the custard is made, you just leave it in the fridge though if you forget about it and remember a week later you have custard in the fridge you should throw it away rather than attempt any ice cream making - eggs and dairy can give you a dodgy tummy if they go off.
When you're ready to tackle the final stage of ice cream production, you have three options:
1) If you have an ice cream machine, lucky you! This will churn and cool your custard base within 30 minutes. Job done, go and make yourself a cocktail.
2) If you're without a machine (as most of us are) then you have a further two options - the first is to put your custard base in a freezer-proof bowl and place in the freezer. Take this out every 15 minutes or so, and stir well, bringing in the mixture from the edges to break up the ice crystals starting to form on the perimeter of the bowl. This distributes the cooler liquid on the outside edges throughout the custard so you get an even 'freeze'. Depending how cold your freezer is, this will take a couple of hours.
3) Alternatively, Peter Barham suggests you use a 'freezing mixture' which is the speediest option for a neophyte ice cream maker not in possession of a fancy machine. All you do is get 1 kg of ice, crush it and place in a large plastic washing bowl, then add 200g salt dissolved in 300ml water. Salt lowers the temperature of the ice and creates an instant ice bath for freezing your custard mixture, which is ideal as the faster the custard freezes the better the texture will be. So place your custard mixture in a metal baking tin and float on top of the ice bath, making sure you don't get any salty water in your custard! Carefully scrape the bottom of the baking tin every few minutes to circulate the cooler liquid and break up those ice crystals, and voila! within 30 minutes you have ice cream.
Finally there is an option for the more adventurous (read: mischievous) amongst you. Persuade one of your willing and able scientist friends to procure some liquid nitrogen and add this to your custard mixture. Plumes of 'smoke' will add to the theatre of this, but the key is within seconds you'll have ice cream. Needless to say, this would be a great way to impress a date, or at least impress a date who's impressed by geeky science (I'd be impressed...)
In principle, ice cream - like baking - is easy. The chemistry of ice cream is complex, especially for a non-sciencey anthropologist like me, but all you have to do is follow the formula of an ice cream recipe. Test recipes and try other flavours as suggested below. If you're a keen bean, then check out the three sources I mentioned above, they're all invaluable guides to the science - and art - of ice cream.
Some flavour ideas:
* instead of infusing your custard with vanilla or chocolate, how about herbs such as fresh bay leaf or rosemary?
* experiment with spices - try cinnamon, cardamom, nutmeg or star anise - infusing these in the custard for the required time and then sieving them out before you freeze and beat the mixture.
* try adding a fruit puree - though be careful they don't have a high water content as this will result in watery, and potentially crystal-dense ice cream. It's worth cooking the puree and allowing all excess liquid to evaporate so you get a concentrated fruit taste. Try summer berries, peach, apricot, apple, banana (this won't really require cooking, just mash and add to the custard), passionfruit, rhubarb. These can also be made into sorbets.
* add praline mixtures, marshmallows, bits of cookies, brownies or leftover christmas cake, the latter makes a great post-Christmas treat, a bit like rum & raisin ice cream.
* you can add alcohol to the mixture, though be wary of adding too much as this will impair freezing. A great example of this is Heston's Kirsch ice cream in the 'Big Fat Duck Cookbook' - a really delicate flavour, and the custard is made with sour cream instead of regular cream.
* last but not least, savoury ice creams are seriously good - these take a bit of getting used to, but if you can get your head around eating salty ice cream (think salted butter caramel, but with less sugar) then give it a go. Chefs have been doing it for years and they've proved increasingly popular.