Warm up the milk and water in the microwave for 30 seconds.
Add the yeast and sugar, and let it sit for 5 minutes until foamy.
Soften the 2 tbsp of unsalted butter.
Add the salt, softened butter, and egg to the yeast mixture and mix.
Add 1 cup of flour at a time, mixing to combine, until you've used about 2.5-3 cups of flour.
Knead the dough for 5-8 minutes, adding more flour as needed when it gets sticky.
Place the dough in an oiled bowl, cover, and let rise for 1 hour.
Divide the dough into 6-8 equal pieces and shape into balls.
Place the shaped buns on a parchment-lined baking sheet, cover, and let rise for 30-45 minutes.
Make an egg wash by whisking together 1 egg yolk and 1 tbsp milk.
Brush the buns with the egg wash and sprinkle with sesame seeds.
Bake at 375°F for 15-18 minutes until golden brown.
