Start by activating the yeast. In a bowl add 1 cup milk, sugar, and lukewarm water and mix. The water should be around 35 degrees or warm enough that you can keep your finger in the water and yet feel the warmth. Add the yeast and mix. Set aside for 5 minutes to bubble up.
Sift the flour into the food processor, add the salt. Slowly add the activated yeast mixture and work on the dough until it comes together.
Remove and transfer to a pastry board or a large, shallow bowl. Press the butter into the dough and knead for 10 minutes.
Cover with a damp muslin and let it proof for 1 hour in a warm place.
After an hour, knead the dough again for 5 minutes to punch out the air. Divide the dough into 4 equal parts. Shape each portion into a bun.
Line the baking tray with a cookie sheet and place all 4 buns on it at a distance. Using the remaining 1/2 cup milk, brush the top of the buns with milk. Cover and let it proof again for 40 minutes. I kept them in the microwave (switched off of course!)
Brush again with the milk wash and top with sesame seeds. Let them stand for another 10 minutes.
Meanwhile, preheat the oven for 10 minutes at 200 degrees.
Place 1 cup water in a bake-proof tray on the bottom-most shelf of the oven. Place your baking tray on the middle shelf and bake for 15 minutes. The addition of water creates moisture and ensures soft buns.
Remove the water and bake for another 10 minutes.
Rest for 5-10 minutes on a wire rack before using it.