Main

1. Combine dry yeast with 15 g of the sugar in a large bowl; pour in warm milk (body temperature) and stir to dissolve.
2. Add about 100 g of the flour to the yeast mixture and whisk until smooth to make a sponge; cover and place in a warm spot to rise about 30 minutes.
3. In a separate large bowl beat the remaining sugar with whole eggs and egg yolks until light and airy.
4. Melt the butter, cool slightly, stir in the sour cream and add this mixture into the beaten eggs, mixing to combine.
5. Sift and add the remaining flour in portions into the egg mixture, mixing and kneading to form a soft dough.
6. Add the risen sponge (opara) to the dough and knead until smooth and elastic, mixing a minute or so and repeating as needed.
7. Let the dough rest in a warm place until it increases about twofold.
8. Soak raisins and candied peel for 30 minutes, drain, then fold them into the risen dough along with vanillin and a pinch of salt.
9. Divide the dough into baking pans of the same size, shape as desired, and allow the filled pans to rise again until nearly doubled.
10. Bake in a preheated oven at 180°C for 35–40 minutes until done; do not open the oven while baking.
11. Remove loaves from pans and cool before slicing and serving.