Ingredients (to make about 2 pints each of two different flavors, vanilla and strawberry):
4 eggs
450ml/1 pint heavy whipping cream
300g/1 pint strawberries
250g granulated sugar
16g/2 packets vanilla sugar (or 1 tsp. vanilla extract)
Separate the eggs. Add 50g sugar to the egg yolks and stir them in a bain marie. If you do not have one per se, you can just put a saucepan with water, which you bring to a boil, and then another saucepan placed on top (and into the lower one) with the ingredients, as in this picture:
Stir continually for a few minutes, until the sugar is dissolved and the egg starts to thicken slightly. This will pasteurize the eggs. Don't leave it until it gets lumpy!
While the egg yolk and sugar mixture is cooling, beat the cream until it is stiff. In the second bowl, beat the egg whites and gradually pour in the rest of the sugar (as if you were making meringues, for those who have done that). When the egg yolk mixture is cool, add it to the egg white mixture and stir it in. Then add the cream and stir it in, until it is homogeneous. Finally, add the vanilla sugar or vanilla essence.
That is the basis for all ice creams, and it is only from this point that they diverge as you may wish to add different flavors, whether chocolate, rum and raisin, crumbled Heath bars or Oreos, or anything else.
For the strawberry ice cream, the next step is to chop them very finely in a food processor.
Obviously raspberries, cherries, and other fruits may be substituted. Take half of the base ice cream mixture and mix it gently together with the strawberries.
You now have a batch of vanilla ice cream and a batch of strawberry ice cream ready to go in the freezer.
After an hour and a half or so, take the bowls out and stir them, before returning them to the freezer. This is crucial to ensuring that they freeze evenly and preventing ice from forming that will make the ice cream's texture less smooth.
Stir them again every hour. The last time I made it, the strawberry ice cream was ready in about 3 hours, and the vanilla in about 5 hours. The difference in time is because of the different compositions (the strawberries contain water) and probably also the different material the bowls I used were made from.
Before they get very hard, transfer them to plastic containers with lids, and they can now stay in the freezer until you are ready to eat them. They shouldn't stay in the freezer for more than a month - not that it is likely that you could wait that long before eating them in their entirety!
Your teenager can help, even with their cellphone in their hand, which is good news, because participating in making ice cream for the first time is precisely the sort of thing they will want to share on Snapchat!