Combine milk, water, yeast and sugar. Let rest 10 minutes until bubbles and foam appear.
Add salt, egg, butter, and flour to the yeast mixture and mix until a soft dough forms.
Knead for 10 minutes until you have a soft, smooth dough.
Cover and let rise for 1 hour.
On a lightly floured surface, divide dough into 6 equal portions.
Flatten each piece and roll into a log, tucking the seams.
Place on a lined or greased baking sheet, an inch apart.
Let rise for 30 minutes.
Score the tops of each bun with a serrated knife (optional).
Bake at 425°F for 10 minutes.
Rotate and bake for an additional 7-9 minutes.
Remove from oven and allow to cool completely before eating.
Butter the tops of the buns immediately after they come out of the oven.
