Passion fruit citrus sodas

1. Put the lemon rind, water and sugar into a stainless steel or enamel saucepan. Bring to the boil, stirring to dissolve the sugar, and boil for 1 minute. Remove from the heat and leave to cool for about 30 minutes, then cover and refrigerate for about 1 hour, or until the mixture is very cold.

2. Meanwhile, cut each passion fruit in half and scoop the seeds out with a teaspoon into a nylon sieve placed over a bowl. Rub the seeds firmly in the sieve with the back of a stainless steel spoon to squeeze out all the juice, then discard the seeds.

3. Strain the chilled lemon syrup into the bowl with the passion fruit juice, then strain in the lemon juice and the lime juice and stir the mixture well.

4. Put 3 ice cubes into each of four tall glasses. Ladle a quarter of the fruit juice mixture into each glass and drop a slice of lemon and lime into each one. Top up the glasses with the soda water, stir quickly and serve immediately while still fizzing.

You can prepare the passion fruit and lemon mixture up to 6 hours in advance, if this is more convenient. Cover the bowl and keep it in the refrigerator. Mix it with the ice and soda water just before serving. You can make up the passion fruit mixture into a hot drink; just dilute it with hot water instead of soda water, remembering to use heatproof glasses. Passion fruits can be very tart before they are ripe. If you cannot wait for them to ripen completely, you may need to add a little more sugar.