Whisk together all of the dry ingredients in a mixing bowl.
Melt butter in a small saucepan on stovetop over medium heat. When it has melted, add the milk and leave it until it's just warm. (110°F / 43°C)
In the stand mixer with the mixing paddle, beat the eggs, egg whites, and vinegar on low-medium speed. Pour in the melted butter-milk mixture once it has reached the correct temperature. Continue to beat for one minute.
Add the dry mixture to the wet in the stand mixture. Beat slowly at first until the flour is incorporated, so it doesn't fly around. Then turn up speed to medium speed and run for 5 minutes.
Meanwhile, grease only the bottom of a 9" X 5" loaf pan.
Scrape batter into prepared loaf pan. Let it sit in a warm place to rise until doubled in size, about 40 minutes.
Preheat oven to 325°F (163°C). Bake loaf for 1 hour or until brown and crusty on the outside. It should seem a little hollow if you tap it.
Allow to cool before slicing, if you can wait that long!