In the steel bowl of your stand mixer, mix together 3 cups flour, salt, sugar and instant yeast. Set aside.

In a pan warm together water and butter till the butter melts.
Let the mixture cool down a bit for 6-7 minutes or till it reaches around 120-125 F degrees.

Add the cooled water-butter mixture now to the flour mixture and mix. Add the whisked egg and mix.

Start adding the remaining flour little by little, 1/4 cup at a time. Stop adding the flour, when the dough just starts coming together from the sides. You may nor may not need all the flour. Do not add more flour than required. The dough will be little sticky and shaggy. That is okay.

Knead on medium-low speed for around 10 minutes using the dough hook attachment of your stand mixer.
The dough will be really soft and little sticky but after you have kneaded it well, it will look totally smooth

Transfer this dough to a oiled bowl, cover with a kitchen towel and keep at a warm place for 1-2 hours or until double in size. If it's really cold when you are making these buns, preheat oven to 200 F degrees and then switch if off. Place the dough inside the oven (with the oven being off) and let it rise there.

After the dough has risen, punch it down to release the air.
Divide it into 10 equal portions. You can use a kitchen scale to make sure all dough balls are equal. Roll each dough portion into a ball and place on baking sheet, around 3 inches apart.

Once you have made all the dough balls, cover with a kitchen towel and let them rise for an hour or till almost doubled in size. Meanwhile preheat oven to 400 F degrees.

Once the dough balls have risen, brush each with egg wash, sprinkle sesame seeds on top.
Bake at 400 F degrees for 12 minutes, rotating once in the middle. The tops of the buns will appear golden brown when done.

Remove from oven, brush them immediately with melted butter. Transfer onto a wire rack to cool completely.