Melt the butter in a saucepan, in low heat.
Take the pastry out of its package. It is necessary to keep the pastry sheets covered with a wet, clean towel, so that they do not get dry and break while you use them.
You will need a thin wooden rod. Alternatively, use a very thin metal rod or a large knitting needle.
Spread two sheets on the kitchen worktop, one on top of the other. With the narrow side facing you, turn the sheets by 10 cm, as if you were folding them. Sprinkle the ground pistachio kernels along the long side of the sheet, approx. until the middle. Place the rod along the sheet, where you folded it, and loosely roll the sheet on the rod. Holding down with your fingers one side of the roll, press and tuck the sheet lightly.
Carefully push the Saragli on the rod.
Place it in a small baking pan. Prepare the remaining Saragli in a similar way. There will be 6 in total, 2 from each kind (pistachios, walnuts, almonds). Place them in the baking pan alternatively, side by side.
Preheat the oven at 150°C for 1.5 hours, with extra heat on the oven elements. Cut the Saragli all the way through, in 1.5 – 2 cm slices. Gradually pour all the butter over the Saragli, making sure to cover the entire surface.
Bake the Saragli on the bottom rack, for approx. 90 minutes, until golden brown and baked to the core.
Take it out of the oven and gradually pour the syrup on top with the ladle, while still hot, until it absorbs all the syrup.
Make sure not to pour all the syrup at once, but little by little. Leave the Saragli to cool down and the syrup to thicken, and serve.