Sift flour and icing sugar into bowl, rub in butter. Add egg yolk and enough water to mix to a firm dough. Roll dough out onto floured surface, large enough to line 23cm flan tin. Cover pastry with greaseproof paper, cover paper thickly with beans or rice. Bake in moderately hot oven 7 minutes, remove paper and beans, bake further 7 minutes; cool.

Fill pastry case with rockmelon mixture, refrigerate until set, top with rockmelon balls, brush with jam mixture, refrigerate 1 hour until set.

Scoop melon into balls. Scoop out remaining flesh, chop roughly; reserve ½ cup. Blend or process reserved rockmelon with sugar, orange rind and juice. Sprinkle gelatine over water, dissolve over hot water (or microwave on high 40 seconds), cool to room temperature, add to melon mixture; stir in cream. Heat jam in pan, strain, stir in Grand Marnier.