Preheat the oven to 175°C using top and bottom heat.
Line a baking sheet with parchment paper.
Place the softened butter and sugar in the bowl of a food processor or in a mixing bowl.
Beat the butter and sugar together until the mixture is light, creamy, and almost white in color.
In a separate bowl, combine the flour, baking powder, cinnamon, and a pinch of salt.
Add the flour mixture gradually to the butter and sugar mixture.
Mix until the ingredients are combined and a dough begins to form.
In a small bowl, beat the egg together with the milk.
Add half of the beaten egg and milk mixture to the dough.
Mix until the dough comes together evenly.
Reserve the remaining egg and milk mixture for brushing the top of the dough.
Place the dough on the prepared sheet of parchment paper.
Roll the dough into a rectangle approximately 1/2 cm thick.
Brush the top of the rolled dough with the remaining beaten egg and milk mixture.
Sprinkle the pearl sugar or sprinkle sugar evenly over the top.
Scatter the almond shavings evenly over the sugared dough.
Transfer the baking sheet to the preheated oven.
Bake for 15 to 20 minutes, or until the cookie slab is golden brown and the almonds are lightly toasted.
Remove the baking sheet from the oven.
While the cookie slab is still warm, cut it immediately into rectangular cookies.
Transfer the cookies to a cooling rack.
Allow the cookies to cool completely before serving.