In a large mixing bowl, combine 2 cups of all-purpose flour, ¼ cup of granulated sugar, 1¼ teaspoons of active dry yeast, and ½ teaspoon of salt.

In a separate bowl, whisk together 1 large egg, ½ cup of whole milk (warmed), and ¼ cup of softened unsalted butter.

Pour the wet mixture into the dry ingredients, mixing until a dough forms.

Knead for about 8–10 minutes until a smooth, elastic ball forms, then let rise for 1 hour in a greased bowl covered with a damp cloth.

In a saucepan, combine 1 cup of whole milk, ½ cup of granulated sugar, 4 large egg yolks, 1 teaspoon of vanilla extract, and 2 tablespoons of cornstarch.

Cook over medium heat, stirring constantly for 5–7 minutes until thickened.

Transfer custard to a bowl, cover with plastic wrap, and let cool at room temperature.

Once the dough has risen, punch it down and roll it into a 12x16 inch rectangle.

Cut the dough into 3x3 inch squares.

Place a dollop of raspberry jam and cooled custard in the center of each square, fold corners toward the center, and pinch to seal.

Place shaped buns on a parchment-lined baking sheet, leaving space for expansion.

Preheat your oven to 200°C (390°F) and let the buns rest for 20 minutes.

Brush each bun with an egg wash made from the reserved egg mixed with a tablespoon of water.

Bake for 15–18 minutes until golden brown.

Let the buns cool on a wire rack for 10 minutes before serving.

Serve warm, optionally dusted with powdered sugar or a light glaze.