1. Heat milk until lukewarm. In a mixer with a dough hook, combine flour, sugar, yeast, cardamom, and salt. Add milk and 1 egg, knead 8 minutes on low.

2. Add butter and knead 5 more minutes on medium until elastic and slightly sticky.

3. Transfer to a greased bowl, cover and rise for 1 hour until doubled.

4. Make the filling by mixing butter and brown sugar. Chop frozen raspberries.

5. Roll dough into a 20×15 inch rectangle. Spread filling and scatter raspberries.

6. Roll into a log and cut into 12 even pieces.

7. Place on parchment-lined baking sheets. Cover and let rise 40 minutes.

8. Meanwhile, whisk yolks, sugar, and cornstarch. Heat milk with vanilla, then slowly whisk into egg mix.

9. Return to heat and cook until thickened (5–8 min). Let cool.

10. Make a well in each bun and fill with 1–2 tbsp custard.

11. Brush tops with egg wash and bake at 400°F (200°C) for 15 minutes.

12. Cool slightly before serving.