Put the milk, sugar and cream into a stainless steel saucepan with the ground cardamom, stir until the sugar has dissolved and the mixture is warm to the touch. Remove from the heat and leave to sit to infuse while you dissolve the gelatine. Sponge the gelatine in a small bowl with 4 tablespoons (4 American tablespoons + 4 teaspoons) of cold water. Put the bowl into a saucepan of simmering water until the gelatine has melted and is completely clear. Add a little of the infused milk mixture and stir well and then mix this into the rest. Beat the yoghurt lightly with a whisk until smooth and creamy, add into the cardamom mixture. Pour into a well oiled ring mould or 8 individual moulds. Allow to set for several hours, preferably overnight.
Just before serving, slice the strawberries lengthways, sprinkle with a little castor sugar and toss gently. Spoon the sugared strawberries into the centre of the ring mould over the top of the yoghurt and cardamom cream. Decorate with sprigs of fresh mint or lemon balm. * To crush cardamom seeds, remove the seeds from 6 or 8 pods and crush the seeds in a pestle and mortar or between 2 sheets of silicone paper with the bottom of a saucepan.