Dissolve the yeast in warm water with a pinch of sugar and let it sit for about 5 minutes until frothy.
In a mixing bowl, combine the flour, sugar, and salt. Add the yeast mixture, beaten egg, and softened butter. Mix until a dough forms.
Knead the dough on a floured surface for about 5-10 minutes until smooth and elastic.
Place the dough in a greased bowl, cover with a damp towel, and let it rise in a warm place for about 1 hour or until doubled in size.
Punch down the dough and divide it into 4 equal portions. Shape each portion into a ball.
Flatten each dough ball into a small circle and place a spoonful of red bean paste in the center. Fold the edges of the dough over the filling and pinch to seal.
Place the Anpan on a baking sheet lined with parchment paper, cover, and let them rise for another 30 minutes.
Preheat the oven to 350°F (180°C). Brush the Anpan with beaten egg for a shiny finish.
Bake for 15-20 minutes or until golden brown.
Let the Anpan cool slightly before serving. Enjoy
