Rhubarb spritzer (Rhabarberschorle)

1. Wash the rhubarb, discard the leaves and cut the stalks into 2 cm pieces - red stalks give a lovely pink colour.

2. Bring the rhubarb to the boil with the water, sugar and scraped vanilla pod and simmer for 10 minutes until it completely falls apart.

3. Strain through a fine sieve or a clean tea towel - don't press, so the juice stays clear - then stir in the lemon juice.

4. Let the syrup cool completely and chill for at least 1 hour.

5. Put ice into the glasses, fill them a third full with rhubarb syrup and top up with well-chilled sparkling water.

6. Garnish with mint leaves and serve.

Tip: Don't throw away the strained rhubarb pulp - it makes a great compote for yoghurt or pancakes.