1
Gently melt the butter and milk together in a pan over a low heat until the butter has melted. Set aside until lukewarm (about 40°C/100°F).
2
Mix the flour, yeast, caster sugar, salt and cardamom together in a large bowl. Make a well in the centre and pour in the beaten egg and yolk followed by the warm milk and butter mixture. Use a wooden spoon to mix until you have a slightly sticky dough.
3
When the dough has taken shape, turn out onto a floured surface and knead for about 10 minutes until smooth and springy. (Alternatively knead in a stand mixer with a dough hook for 4-5 minutes.) Dust with flour if you find the dough too sticky.
4
Transfer the dough to a clean greased bowl, cover with a damp tea towel and let it rise in a warm place for 1 hour, or until it has doubled in size.
5
For the filling, beat all the ingredients in a bowl until you have a smooth paste.
6
When the dough has risen, punch it down in the bowl and tip onto a lightly greased work surface. Roll into a rectangle 45 x 30cm (17 x 12in) and about 5mm (¼in) thick. Spread the filling all over and then, starting from one long side, roll the dough into a cylinder. Use a sharp knife to slice into 12 equal-sized pieces.
7
Lightly grease a roasting tray that is about 25 x 20cm (10 x 8in) and place the rolls in, cut-side up. Cover with lightly greased cling film and leave to rise for around 30 minutes in a warm place until puffy.
8
Preheat the oven to 200°C/180° fan/400°F/Gas 6. Brush the buns with the egg, sprinkle with the sugar and bake for 15 minutes, or until golden brown.
9
Leave the buns to cool in the tin for 10 minutes, then transfer to a wire rack to cool a little before serving.