Vanilla slice

Method

1. Heat the oven to 180°C fan/gas 6. Roll out the pastry sheet until 40 cm long and at least 20cm wide (though it can be trimmed once cooked), then put on a large baking tray lined with baking paper. Cover in another sheet of baking paper and the second tray, which will keep the pastry flat and encourage a nice even bake. Bake for 25 minutes or until the pastry is golden and cooked through, then remove and leave to cool on a wire rack.
2. Soak the gelatine in a small bowl of water for 5 minutes to soften. Put the milk and cream in a saucepan over a medium heat and bring to just below boiling point. Whisk the cornflour, sugar, egg yolks and vanilla to a thick paste in a large heatproof bowl, then gradually whisk the warm milk into the cornflour mixture until smooth (it might be lumpy at the start but the lumps will dissipate as you slowly add more liquid).
3. Return the milk mixture to the saucepan, then set on a medium heat and bring to the boil, whisking constantly until thickened (about 5 minutes). Squeeze the excess water from the gelatine, then stir into the pan with the butter and whisk until melted, then remove from the heat.
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5. Using a serrated knife, trim the pastry to give 2 squares of pastry that will fit the prepared tin (2 x 20cm x 20cm). Put 1 piece in the base of the prepared tin, then pour over the custard and top with the other sheet of pastry. Cover and chill until firm (about 4 hours or overnight).
6. To make the icing, whisk 200g of the icing sugar with 40ml of the juice or water until smooth. In a separate bowl, whisk the remaining icing sugar with the remaining juice or water and a little food colouring until smooth.
7. Pour the white icing over the cool pastry and spread using a palette knife or the back of a spoon to cover evenly. Scrape the coloured icing into the piping bag and pipe lines across the top, 1cm apart. Take your cocktail stick and drag it through the lines of icing to create the classic decoration (it’s known as feather icing). Leave to set (about 30 minutes). Once set, use a serrated knife to cut the custard pastry into into 2 halves, then cut each half into 4 even slices.