3: Cover the bowl with stretch film, making sure it seals well.
4: Sit the bowl over a pan of water to form a bain-marie. Leave on low heat for 40 minutes.
5: The plastic film will swell into a dome and collect condensation. If you want to see what's going on underneath, tap on it gently.
6: After 40 minutes, take the bowl out of the bain-marie and leave to cool with the film still in place. When cold, remove the film. You will see the strawberry pieces have softened and are bathed in juice.
7: Pour everything through a fine strainer sitting over a bowl and leave to drain.
8: Collect the juice and pour into a jar with a lid that seals well. Refrigerate until needed.
Remarks
Use the strawberry pieces leftover for another recipe, or simple eat them yourself! (They're good with a little fromage frais).