In a large mixing bowl, combine 3 cups of all-purpose flour, ¼ cup of granulated sugar, and 1 packet of active dry yeast.

Heat 1 cup of milk until warm (not hot), then mix in 1 beaten egg and ½ cup of softened unsalted butter.

Gradually pour this mixture into the dry ingredients, stirring until a soft dough forms.

Knead the dough on a floured surface for about 10 minutes, then place in a greased bowl.

Cover with a clean cloth and let it proof in a warm area for about 1 hour, or until doubled in size.

While the dough is rising, prepare the custard filling. In a saucepan over low heat, whisk together 1 cup of milk, ¼ cup of granulated sugar, 3 egg yolks, 2 tablespoons of cornstarch, and 1 teaspoon of vanilla extract.

Stir continuously for about 5-7 minutes until the mixture thickens to a custard-like consistency.

Once thickened, remove from heat and let cool completely.

After the dough has risen, punch it down gently and divide it into 8 equal portions.

Roll each portion into a circle about 6 inches in diameter.

In the center of each circle, place a spoonful of custard and a dollop of raspberry jam.

Carefully fold the dough over the filling, pinching the edges to seal the buns tightly.

Arrange the shaped buns on a parchment-lined baking tray, cover with a cloth, and let them rest for about 30 minutes.

Preheat your oven to 200°C (400°F). Brush the buns with an egg wash and bake for 15-18 minutes, or until golden brown.

Allow them to cool on a wire rack for about 10 minutes, then dust with powdered sugar before serving.