In a large, wide bowl, mix the salt and flour.
Use your fingers to work the butter into the flour.
Dissolve the yeast in the milk.
Add the eggs and dissolved yeast to the flour mixture. Mix well, then knead on the counter for about 20 minutes, until you have a smooth dough. Return the dough to the bowl and cover.

Let the dough rise for about 2 hours, until it doubles in size.
Divide the dough into 6 pieces and shape each into a ball. Flatten slightly and place on a baking sheet greased with a little oil or butter.
Cover the baking sheet loosely with plastic wrap. Let the buns rise for about 2 hours, depending on room temperature, until doubled in size.
Preheat the oven to 380°F (194°C).

Once the buns have finished rising, lightly beat the egg white with the water. Brush the tops of the buns with the egg wash.
Sprinkle with sesame seeds and poppy seeds if desired.
Bake in the oven for about 25 minutes, until the tops are a deep golden brown.

You can watch this recipe on YouTube.
https://youtu.be/OLFG5Ueek0M