Pick over 225g (8 oz) fresh raspberries and then mash them down in a saucepan. Add 2tablespoonsredcurrant jelly and stir over low heat until the jelly has melted and the raspberries are quite soft. Blend 2 level teaspoonscornflour with 1tablespoon cold water and stir into the contents of the pan. Stir until boiling, when the mixture will thicken and become clear. Strain into a basin, add a squeeze of lemon juice to sharpen the flavour and serve warm or cold.