In a small bowl, combine warm milk, sugar, and instant yeast. Allow to sit for about 5 minutes until foamy.

In a large mixing bowl, whisk together all-purpose flour and salt. Pour the yeast mixture, sweetened condensed milk, egg, and softened butter into the flour. Mix until dough forms, then knead for 8-10 minutes on a floured surface.

Place the dough in a greased bowl, cover with a damp kitchen towel, and let rise in a warm area for 30-45 minutes, or until doubled in size.

Gently punch down the dough to release air, shape into a loaf or 8 pieces for buns. Place in a greased pan or on a baking sheet and let rest for 15-20 minutes.

Preheat the oven to 350°F (175°C). Whisk the egg and brush over the dough for finish, then bake for 25-30 minutes until golden brown.

Let the bread cool in the pan for 10 minutes before transferring to a wire rack to cool completely. Slice and serve.