Mix together the warm water, milk, yeast and sugar. Set aside for 5 minutes until you see a foam on the top. If you don't have a foam, do not proceed. This is a crucial part of having fluffy buns.
Add in the flour, salt, butter and a beaten egg. Mix until the dough forms. You want the dough to be soft but not sticking to your fingers. If you need to add more flour, sprinkle in a few extra tablespoons at at time.
Cover the bowl with a towel and let it sit somewhere warm for around 1-3 hours or until doubled in size.
Once the dough has doubled in size, flip it out onto a floured surface. Divide into 8 equal pieces.
Shape the dough into balls, gently flattening and tucking the ends underneath.
Place the dough balls onto a baking sheet that is lined with parchment paper.
Cover and let them rest an additional 1 hour or until they're fluffy in appearance.
Make the egg wash by beating the egg and water together. Gently brush the top of the buns with the egg wash and sprinkle with sesame seeds.
Preheat your oven to 400 degrees. IN the bottom of your oven place a baking sheet or dish. Right before you put your buns in, pour 1/2 a cup of water in the pan to create steam. This will make your buns fluffy and moist.
Bake the buns for 15-20 minutes or until they're golden brown on top.
Take them out and let them cool slightly before serving.