Wash the oranges and, using a sharp knife, cut off the upper quarter. Carefully hollow out the oranges. Cut Halloween-style faces in the orange skins. Squeeze the orange flesh to produce as much juice as possible and put into a measuring jug.
Cut up the jelly squares and put in a bowl. Pour over 284ml of boiling water and stir to dissolve. Allow to cool but not set. Make up the orange juice in a separate bowl to 284ml if necessary with cold water, and add to the jelly, stirring. Chill in the fridge until fully set.
Spoon the jelly into each orange head, put the cut off top back on. Wrap each orange in cling film, twisting at the top, and chill in the fridge until ready to serve.
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