Melt butter in milk over low heat.

Pour mixture into a bowl and let cool slightly.

Whisk in egg yolks.

Whisk in yeast and let stand until foamy, about 5 minutes.

Whisk flour, sugar, and salt in a large bowl.

Stir in milk mixture until a wet dough forms.

Beat egg whites until stiff peaks form.

Fold egg whites into the dough.

Scrape dough into a greased bowl.

Shape dough into a round loaf.

Cover and let rise in a warm place until doubled, about 2 hours.

Butter a 10-inch tube pan.

Punch down the dough and create a hole in the center.

Transfer dough to the prepared pan, inserting the tube into the hole.

Pat the dough to the sides of the pan.

Cover and let rise until nearly doubled, about 1 hour.

Preheat oven to 325°F.

Bake for 25 minutes, until a crust starts to form.

Increase oven temperature to 375°F and bake for 20-25 minutes longer, until golden and crusty.

Let cool in the pan for 10 minutes.

Remove bread from the pan, slice, and serve warm.