In a large mixing bowl, combine all-purpose flour, sugar, active dry yeast, and warm whole milk. Stir until well combined. Knead for about 8-10 minutes until smooth and elastic.

Place the kneaded dough in a warm, covered bowl to let it rise until doubled in size, about 1 to 2 hours.

In a saucepan over medium heat, whisk together whole milk, egg yolks, sugar, and cornstarch until thickened, about 5-7 minutes. Stir in butter and vanilla extract and let cool.

In another saucepan, combine raspberries, sugar, cornstarch, and lemon juice. Cook over medium heat until thickened, about 7-10 minutes. Let cool.

Punch down risen dough, divide into portions, flatten each, and scoop custard and raspberry filling into center. Seal and place seam-side down on parchment-lined tray.

Cover the shaped buns with a towel and let rest for about 30 minutes.

Preheat oven to 350°F (175°C). Brush buns with egg wash and bake for 18-20 minutes or until golden brown.

Let cool slightly, then dust with powdered sugar before serving.