Jiggly & Fluffy Taiwanese Castella Sponge Cake Recipe

👩‍🍳 Castella Sponge Cake 古早味蛋糕食谱 👨‍🍳Makes 1 (6 inch square cake pan)(A)70g salted butter 牛油10g golden granulated sugar 糖 70g whole or semi skimmed milk 牛奶4 large egg yolks, cold 蛋黄 (冷)70g cake flour 低筋面粉 1 tsp vanilla extract 香草精(B) 4 large egg whites, cold 蛋白 (冷)1 tsp white vinegar 醋70g golden granulated sugar 糖 Baked (in hot water bath) preheated oven at 150°C for 60 minutes.预热烤箱150℃热水浴烘烤60