Step 1: Flour and salt should be combined in a big mixing bowl. Mix the flour and one-third of the butter until the mixture resembles breadcrumbs. Next, roughly mix in the remaining butter, leaving large lumps.

Step 2: Water can be added gradually until the dough comes together. Turn out the dough onto a floured board and roll it into a thin rectangle about 2.5 cm/1 in thick. 

Step 3: Wrap the pastry in plastic wrap and refrigerate for ten minutes. Three more times, roll and rotate, allowing the food to cool in between.

Step 4: While the pastry is resting, prepare the crème patissière. In a bowl, whisk together the egg yolks, sugar, and cornstarch. Combine the two mixtures, cook until thickened, and then stir in the butter.

Step 5: Cover the chilled crème patissière with plastic wrap and store it in the fridge.

Step 6: It is necessary to preheat the oven to 220C/425F. Arrange two pastry trays in a line.

Step 7: Divide the pastry in half, then roll out each half to a thickness of 20 cm by 8 in by 5 mm. Put in the fridge for ten to fifteen minutes.

Step 8: Bake the pastry sheets until they become firm and browned. Calm them down. Line a baking sheet that is 23 cm/9 in square with aluminum foil.

Step 9: Evenly spread the crème patissière, then cover with the second pastry layer. While making the frosting, place it in the refrigerator. Sift the confectioners’ sugar and stir in the lukewarm water to make the frosting.

Step 10: Pipe parallel chocolate lines onto the frosting using a piping bag. Chill the slice to make it solid. Slice the meat into eight pieces, then put the pieces on a serving dish.