Heat the milk till it is warm to touch (110°F). Take half cup milk and mix in 1 Tbsp of sugar. Sprinkle the yeast on top and set aside for 5 to 10 minutes. The yeast should become active and froth up .
Reserve about 2 C of flour (200g) and place the rest in a large mixing bowl. Add the salt and stir well. Make a well in the center of the flour and add the yeast mixture followed by the eggs. Mix the eggs and yeast with a spoon and slowly start to mix in the flour. Add the remaining milk a little at a time and keep stirring with the spoon until all the flour is wet.
Add the softened butter and sugar and start kneading. The dough will be very sticky. As you knead add the reserved flour a little at a time until the dough is no longer sticky. Keep kneading for about 15 minutes. The dough should be soft and pliable. Form into a ball and place in a large greased bowl. Cover and let it rise for 1 to 1 1/2 hours till it has doubled.
If using the raisins, place it in a bowl and pour the cognac/rum on top. Let these soak till ready to use. Squeeze out the excess alcohol out just before adding to the dough.
Punch down the dough and divide into 2. If planning to add nuts/ dried fruits knead those in now. Form each section into 3 ropes of similar size and make a 3 strand braid. Place each braid in a 9 inch loaf pan and let rise for 30 minutes.
Preheat the oven to 350°F(175°C). Break the egg for the egg wash into a bowl and add 2 tsp water. Beat well. Brush the egg wash on top of the risen loaves. Sprinkle the coarse/nib sugar on top , if desired. Place the loaves in the preheated oven and bake for 30 to 40 minutes or till done(see notes).
Cool in pan for 10 minutes. Transfer to a cooling rack and cool completely.
Use any unbleached, un-bromated high protein flour (AP Flour/ Bread Flour).
The rough weight equivalents are - 750g Flour, 14g Yeast, 8g Salt, 100g Sugar, 230g Milk, 110g Butter.
For detailed instructions go to https://oventales.com/bulgarian-kozunak-a-sweet-bread-inspiration/ .