Malaysian Mexican Butter-filled Buns

Months and months ago, sister S. made this recipe from Jane Mason's The Book of Buns. Ms. Mason says that these buns are sold as "Mexican Coffee Buns" all over Malaysia, and that they are sometimes called Rotiboy buns after a chain that popularized them. I liked them, and have thought of recording the recipe; it was hard for me to find the recipe again because I was remembering them as "Butter-filled Buns," since they are, in fact, stuffed with a little cube of butter.

Scalded dough:
100 g (3/4 c) AP flour
70 g (1/3 c) boiling water

Put the flour into a little bowl and pour over the boiling water. Stir to mix. Cover with plastic wrap and set aside.

Dough:
400 g (3 1/4 c) AP flour
2.5 g (1 1/4 t) instant yeast OR 5g (1 3/4 t) dry yeast OR 10 g fresh yeast
80 g (6 T) sugar
175 g (2/3 c) milk, heated up to just below boiling point, then cooled to room temperature
10 g (2 1/2) t salt
1 egg
60 g (5T) butter, cubed, at room temperature

Put the flour in a big mixing bowl; make a well. Sprinkle yeast and sugar into the well and the pour in the cooled milk. Flick some flour over the milk to seal the well; cover and allow to rest 1 hr.

Add salt, egg, and cooled scalded dough (break it up tin obits so it is easier to incorporate). Bring the ingredients together in the bowl. Turn dough out and knead well 10 minutes. Add the butter and knead again for 10 minutes. Return to bowl, cover; reast for 2 hours. Pull dough out onto an unfloured surface.

Divide dough into 12 equal portions. Roll each portion into a 'tight ball.' Allow to rest under a dry towel for 15 minutes.

Gently flatten each piece of dough into a disk about 1 1/4 inches in diameter. Place in the center one of:

100 g (6 1/2 T) butter, divided into 12 little cubes, at room temperature

Stretch the dough around the butter. Roll it up and shape into a tight ball. Place on prepared baking sheet and repeat with remaining dough. Cover and let rest for 30 minutes.

Prepare topping by beating together:

125 g (8 T) butter, at room temperature
125 g (1 scant cup) powdered sugar
1 egg
240 g (2 c) AP flour
1/2 t pandan paste (optional)

Pipe a thin swirl on top of each bun that starts at the top of each bun in the center and travels one third of the way down the sides. Allow the buns to rest, uncovered, for about 15 minutes.

Preheat oven to 425. Bake the buns 15 minutes. Cool completely on wire rack.