Have all ingredients at room temperature. Measuring the flour by weight in grams/oz which is more accurate than measuring by volume.
6.5 oz (200 ml) warm milk
2 1/4 teaspoon active dry yeast or instant yeast (7 g)
160 g (1 stick+3 Tbsp) unsalted butter in pieces, softened
1 tablespoon (15 g) granulated sugar
3 large eggs
1 teaspoon (6 g) fine salt
600 g (21 oz about 4 1/2 cups) white bread flour or all-purpose flour
1 egg yolk mixed with 2 teaspoons milk for egg wash
2-3 tablespoons sesame seeds
Sprinkle the yeast over the milk (all of it, 200 ml) and set it aside for 5-10 minutes for the yeast to activate and dissolve.
Meanwhile, cream softened butter (not melted) and sugar together with a mixer in a separate big bowl, until light in color, about 3 minutes.
Add the eggs, one at a time.
Add the yeast-milk, salt and about half of the flour. Mix with your mixer on low speed for 1 minute until well combined.
Add the rest of the flour and stir with a cooking spoon until the ingredients come together. Knead the dough with your hands either directly in the mixing bowl or on a lightly floured surface for 5 minutes until smooth. For the first minutes, the dough will be very sticky, but it gets better after a while. Do not add any additional flour as the buns will get tougher. After the first rise, the dough is a lot easier to handle.
Put the dough in a big clean and oiled bowl, and let it rise covered with a lid or cling wrap at room temperature until doubled in volume, about 1-2 hours, depending on the room temperature.
Turn the dough out onto a lightly floured work surface and divide it into 24 equal pieces (a scale helps a lot).
Shape each piece of dough into a smooth, tight round ball and place them onto a baking sheet lined with parchment paper, 3 inch apart. Let the buns rise covered with a tea towel until puffy, about 30 minutes to 1 hour. Instead of covering the balls with a tea towel, you can spray them with a spray bottle filled with water (or brush them with water) to prevent them from drying out.
When puffy, brush the buns in batches of 3 at a time with egg wash and sprinkle with sesame seeds.
Put them in the center rack of the preheated oven and bake them for about 20 minutes at 375 F (200 C) or until golden brown. Transfer the buns immediately to a cooling rack.
When cooled completely, slice the buns in half horizontally and toast before assembling.