Engadiner Nusstorte, sometimes called Bündner Nusstorte, originates from the Engadin valley in the canton of Graubünden. The base is a buttery shortcrust pastry that hides a rich filling of caramelized sugar, cream, honey, and a large amount of chopped walnuts. It is a dessert with a rich flavour and long shelf life.
Quickly process all shortcrust pastry ingredients into a smooth ball (best in a food processor). Be careful not to let the butter get too warm.
Wrap the dough in plastic wrap and chill it in the refrigerator for at least 1 hour. Grease a springform pan (24 cm diameter) with butter.
In a saucepan, melt the sugar with water and let it caramelize to a light brown caramel (do not stir, just shake the pan occasionally).
Remove from heat, slowly pour in the warm cream, and stir until the caramel dissolves and the mixture thickens. Return to low heat and cook for 10-15 minutes until a creamy consistency is reached.
Stir in the honey and chopped walnuts. Remove the filling from the heat and let it cool slightly to thicken.
Roll out two-thirds of the chilled dough and line the bottom and sides of the springform pan (the edge should be about 3-4 cm high). Leave the excess edges for now.
Spread the filling evenly over the dough. Fold the excess dough edge over the filling.
Roll out the remaining third of the dough, cover the tart with it, and firmly press the edges to seal.
Brush the top with the beaten egg and prick several times with a fork (to allow steam to escape).
Bake in the preheated oven at 200 °C (390 °F) for 30-35 minutes until the tart is beautifully golden brown.
Let cool completely in the tin. The tart is best sliced on the second day.