Whisk butter and sugar in a bowl. Pour egg in three separate times in it to be mixed easily. Sprinkle cake flour and baking powder and mix with rubber spatula.
Wrap with plastic wrap evenly, and cool it in a refrigerator.
Divide into 6 balls and put each between plastic wrap. Press with scraper to extend into 6cm in diameter, then cool it in refrigerator.
Mix sugar, salt, yeast and milk (around 40℃) with rubber spatula.
Add egg and mix, then add bread flour and butter and mix.
Knead 2. on a table for 3-4min until elastic using scraper. Add more flour if still sticky. Round the dough and put back in a bowl.
Cover the bowl with plastic wrap and let stand in a warm place for 1 hour to make the dough 1.5 times fermented.
Take out 4. on floured table and make it in stick shape. Cut and round into 6 balls with scraper and put plastic wrap softly.
Press ５. and form into ball shape again. Remove the wrap and put cookie topping on it. Pour granulated sugar in a canister with round mouth, and pinch the rim of cookie topping not to be taken off and put granulated sugar. Make grill pattern with scraper.
Grease pot with butter and place . in it. Cover the lid and let stand in warm place for 30 min until 1.5 times fermented.
Remove the lid, and bake in 170℃ oven for 15min, then lower the heat to 150℃ for 10 min.