Whisk warm milk with sugar and the 75 g condensed milk until the sugar mostly dissolves.

Sprinkle in the dry yeast and crack in the egg; whisk again to combine until tiny bubbles from the yeast start to appear.

Mix flour and salt in the bowl of a stand mixer.

Pour the wet mixture into the dry ingredients and start the dough hook on low; work the dough until it just comes together.

Add the 50 g softened butter in pieces; knead with dough hooks for about 10 minutes until smooth, elastic, and slightly tacky.

Cover the bowl and set the dough aside for 1 hour, or until doubled and jiggly.

Meanwhile, warm a pan of water in the oven if your kitchen is cold.

After the first rise, cut off 2/3 of the dough and roll it into a 25x40 cm rectangle.

Roll up the rectangle into a log, slice into equal pieces, and place them in a prepared baking pan.

Repeat with the remaining 1/3 dough to make smaller buns.

Set the shaped buns aside for a second 1-hour rise.

Preheat the oven to 180°C/350°F.

Brush each bun with egg wash just before baking.

Bake larger buns for 25–30 minutes until the tops are deep golden and sound hollow when tapped; smaller buns need about 20 minutes.

Meanwhile, whisk equal parts of butter and 45 g condensed milk.

When the buns come out, brush them with the butter-condensed milk mix while still warm.

Cool the buns in the molds until fully cooled before removing.