In a large bowl combine the yeast, sugar, 1 teaspoon of the salt and 1 1/2 cups of the flour.
In a sauce pan combine the milk, water and 1/4 cup of the butter or margarine until 38 degrees C (110 degrees F). Add milk mixture and vinegar to the flour mixture and blend at low speed of the mixer until moistened. Beat at medium speed for 3 minutes.
Stir in 1 1/2 cups additional flour to form a sticky dough. Turn dough out onto a floured surface and knead adding 1/2 to 1 cup more of flour until dough is smooth and pliable. Place dough in a greased bowl and let rise in a warm place until doubled in volume.
Punch down dough and roll into a rectangle shape about 40cmx20cm.
In a saucepan heat the onion, garlic, 1/2 teaspoon salt, parsley and 2 tablespoons butter or margarine until butter or margarine is melted. Spread over the dough rectangle and starting from the 40cm side roll the dough up tightly like a jelly roll.
Place the bread seam side down onto a greased cookie sheet and let rise until doubled in sized.
Preheat oven to 200 degrees C (400 degrees F).
Bake bread until golden brown about 20 to 30 minutes. Brush hot bread with melted butter and sprinkle with chopped parsley.