Soak the saffron in 1 tablespoon warm water for at least 30 minutes to release the colour. Pour the water and saffron into the apple juice.
Place 1/4 cup of the juice in a small container and sprinkle the gelatine over - let stand until gelatine is completely absorbed in the liquid.
Heat the remaining juice in a small saucepan until steaming then add the gelatine mixture, stirring constantly until it has completely dissolved.
Add the sherry and cool to room temperature, then pour into a bowl or jelly mould and chill until set. If possible, stir once or twice as the jelly thickens, so that the saffron strands set in suspension rather than falling to the bottom.
Halve and core the pears, then slice lengthwise into narrow wedges.
Melt the butter in a pan and add sugar and cardamom, then pear slices. Shake the pan to prevent sticking as sugar melts, and turn pear slices until golden and sticky on both sides. Lift the cooked pear slices out onto a serving plate, then stir the cream into the caramel in the pan.
When it is well integrated, pour the caramel sauce over the pear slices and serve with the saffron jelly.