Jelly and custard cream slice

Method

• step 1

  To make the jelly layer, put the gelatine leaves one by one into some cold water to soften. Put the berries and sugar in a pan with 200ml water and warm gently until the sugar has dissolved, then bring to the boil for 2 minutes. Take off the heat and mash really well with a potato masher, then press through a sieve into a big measuring jug – you need 500ml. Squeeze the excess water out of the softened gelatine, then stir it into the berry juice until dissolved. Line a 22cm square tin with a double layer of clingfilm (it’s easier if you brush the inside of the tin with a little oil first) then pour in the berry jelly and chill until set.

• step 2

  Heat oven to 200C/fan 180C/gas 6. Roll out the pastry on a sheet of baking parchment to a 30 × 35cm rectangle. Dust with the icing sugar and lay over a second sheet of baking parchment. Lift onto a flat baking sheet and sit another flat baking sheet on top, like a sandwich. Fill a few small tins with baking beans (or something similarily heavy and ovenproof, such as raw rice) and put these on top. Bake for 30 minutes, then have a quick peek – it will probably need another 5 minutes to be well browned and crisp all over, but it’s best to check. Lift the pastry from the oven and carefully remove the weights, top tin and top sheet of parchment. Leave to cool.

• step 3

  When the pastry is cool, use a big, sharp knife and ruler to cut the pastry into two 10 × 24cm neat rectangles, and a third rectangle about 12 × 26cm. Divide each of the 10 × 24cm rectangles into six so you end up with twelve 10 × 4cm pieces. Mix the icing sugar for the icing with about 2½ tbsp water to make a thick, runny icing. Remove a couple of spoonfuls and mix with enough colouring to get a deep pink colour, then transfer this to a small piping bag. Spread the white icing over the 12 × 26cm pastry rectangle, then pipe across thin stripes of the pink icing. Use a skewer or toothpick to drag lines through the icing, at right angles to the pink stripes, to feather the icing. Leave in the fridge until set hard. Cover the other pastry with clingfilm to keep it crisp and fresh.

• step 4

  Whip the cream, custard, mascarpone, icing sugar and vanilla until just holding its shape, then spoon into a big piping bag. Chill until you’re ready to assemble.

• step 5

  To assemble, carefully lift the jelly from its tin. Halve, then divide each half into 6 rectangles; the easiest way to do this is with a big pair of kitchen scissors, cutting through both the jelly and the clingfilm – then you can top each portion of jelly with a piece of pastry, neatly flip and peel off the clingfilm. Trim the edges of the iced pastry to 10 × 24cm, then divide into 6 too. Pipe blobs of the custard cream over each jelly-topped pastry slice, then carefully stack into 6 sandwiches, finishing with your iced pastry top.