Boil soy milk with Earl Grey tea bags to steep.
Sift soybean flour, wheat flour, and baking powder.
Cream butter and sugar together.
Add eggs and mix well.
Pour in the steeped soy milk and Earl Grey mixture.
Add the dry ingredients and gently mix until smooth.
Pour the batter into the pan.
Bake in a preheated oven at 180°C for 35~40 minutes.
Cool completely before serving.