In a small bowl, combine the warm milk with 1 tablespoon of the granulated sugar (taken from the ¼ cup) and the active dry yeast. Let it sit for about 5 minutes until it becomes frothy.

In a large bowl, whisk together the eggs and melted butter. Add the remaining granulated sugar and salt, then stir in the frothy yeast mixture. Gradually add the flour, mixing until a dough forms.

Turn the dough onto a lightly floured surface and knead for about 8–10 minutes until smooth and elastic. Place the dough in a lightly greased bowl, cover, and let it rise in a warm spot for about 1 hour or until doubled in size.

In a small bowl, mix the custard powder with a few tablespoons of milk to form a smooth slurry. In a saucepan, bring the remaining milk and granulated sugar to a boil. Gradually whisk in the slurry, stirring constantly over medium heat until the mixture thickens to a pudding-like consistency. Remove from heat, stir in vanilla extract if using, and allow the custard to cool completely.

Once the dough has risen, roll it out on a lightly floured surface into a rectangle roughly 16 inches square. (If you prefer a thinner layer, aim for about ⅛ to ¼ inch thickness.)

Evenly spread the cooled custard over the dough. Sprinkle the raisins (or your choice of add-ins) evenly over the custard layer.

Cover the pastries lightly with a clean kitchen towel and let them rest for about 20 minutes, allowing a final rise.

Preheat your oven to 375°F. Brush the tops of the pastries with the egg wash (½ beaten egg mixed with 1 teaspoon milk) and sprinkle 4 tablespoons of almond flakes evenly over them.

Bake the pastries in the preheated oven for about 20 minutes, or until they are nicely golden and cooked through.

Remove from the oven and, while still warm, dust lightly with 1 tablespoon of powdered sugar. Allow to cool slightly before serving.