Mix the flour, baking powder, dry yeast, sugar and salt in a bowl. Pour over half of the milk, mix well and let it stand for 15 minutes.
Add the butter and sour cream and work them into the flour mixture. Use your hands to form a crumble. Add milk to knead the dough to a smooth dough. Cover it with a towel and let it sit for 1 hour.
Lightly flour your workface, divide the dough in half and roll out one half into a 30 cm square. Cut into 4 stripes, then cut each strip into 6 equal pieces.
Spoon a little pineapple mixtue into the centre of each rectangle and fold both corners of the long sides and press towards the center. Do the same with the remaining rectangles.
Preheat the oven to 200°C. Brush the cakes with egg yolk and bake the tacos for 20 minutes until golden brown. Let them cool down.