To make pastry: Sift flour into a large mixing bowl; add sugar and combine. Grate cold butter into flour mixture with a grater. Work lightly with your fingertips, rubbing together the butter and flour until the mixture resembles breadcrumbs. (You will find this easier to achieve if you work with your fingers raised above the bowl.) Add egg yolk and mix lightly.
Stir in water, mix with a palette knife until mixture begins to bind together. Do not add more liquid than necessary.
Knead very lightly on a floured surface until pastry is smooth. Pat pastry into a ball; flatten slightly. Wrap in plastic food wrap and place in the refrigerator for 30 minutes to rest before using.
Dust rolling pin lightly with flour, roll the chilled pastry out on a lightly floured board. (keep turning the pastry around so it would not stick to the board or tabletop.)
Roll pastry to 1/4cm thick and large enough to cover a 22cm flan tin. Transfer the pastry by rolling it carefully round the rolling pin. Place the rolling pin on one side of the tin; gently unroll. Ease the pastry gently into the tin and press into the corners of the tin. Trim the edges neatly with a palette knife.
Prick pastry base with a fork. Chill well for 15 to 30 minutes. Line pastry top with tracing paper and fill with some beans or rice. Blind bake pastry case in a preheated oven at 190 °c for 15 minutes. Remove beans and paper and bake for a further 15 to 20 minutes or until golden.
To make custard filling: Combine flour, corn flour, sugar and salt in a medium bowl. Add a little milk into the egg yolk and beat lightly with a hand whisk. Add a little milk to the combined dry ingredients and mix well. Stir egg yolk mixture and remaining milk into the flour mixture.
Strain the mixture into a double boiler pot and add in butter. Keep stirring the mixture constantly until it takes on a thick custard consistency. Add vanilla essence and mix well. Remove custard from heat and leave to cool completely before use.
To assemble fruit flan: Brush inside of baked pastry case lightly with apricot jam. Fill with custard filling. Arrange fruits in any desired pattern.
Glaze fruits with apricot gel. Chill fruit flan in the refrigerator until serving time.
To make Apricot Gel Glaze: Combine well then stir over low heat to dissolve the jam. Strain the jam mixture and use immediately.