Melt the butter in a small saucepan over medium heat. Stir in the milk, sugar and salt.
Remove from the heat and set aside.
In a large bowl, stir together 2 cups of flour, cardamom and yeast.
Pour in the milk mixture and the egg and stir quickly with a wooden spoon until the dough is elastic, about 3 minutes. Gradually mix in the remaining flour until the dough is firm enough to knead on a lightly floured surface. If you have a stand mixer with a bread hook attachment, you may use that instead. Knead or mix dough until small gas bubbles form and dough is smooth, about 10 minutes. Work in the currants at the very end so they don't become pulverized.
Place dough in a greased bowl, turning to coat, and cover the bowl with a towel. Set aside to rise until doubled in size, about 1 hour.
When the dough has risen, punch down and divide into about 16 pieces. Fold into rounded buns and place them on a baking sheet or in a baking dish.
Let rise again until almost doubled in size, or until your finger leaves a dent that does not spring back when you poke the bread.
Preheat the oven to 350 degrees F (175 degrees C). When the oven is hot, bake the rolls for 30 minutes, or until golden brown on the tops.
