In the bowl of a stand mixer fitted with the hook attachment, combine the warm milk (or water), yeast, and sugar. Give it a quick stir to combine then let sit for 5 minutes, until very foamy.
Whisk in the salt and egg.
Add the flour and knead until flour is fully absorbed.
On LOW speed, add the cubed softened butter one tablespoon at a time. Knead an additional 1 to 2 minutes, until a soft and pliable dough.
Cover the bowl with plastic wrap or a damp kitchen towel to rise 45 minutes to 1 hour, until dough has doubled in size.
Preheat oven to 375F. Line a baking pan with parchment paper.
Transfer the dough onto a clean surface. Divide into 8 to 10 equal sized pieces. Roll each into a tight ball.
Evenly distribute on the prepared baking pan. Use a flat spatula or the palm of your hand to press down each ball to 1" thick.
Cover with plastic wrap to rise 30 to 45 minutes, until doubled in size.
Brush the very tops with the beaten egg, garnish with sesame seeds, then bake for 15 to 20 minutes, until deeply golden on top. Rotate the pan halfway through baking. Let rest at least 15 minutes before slicing to enjoy.