Ingredients

• Biscuit sponge
• ¼ cups (30 grams) cake flour, sifted
  
• 2 tablespoons all-purpose flour
  
• ¼ teaspoons fine sea salt
  
• 2 large (113 grams) eggs, at room temperature
  
• 3 large (64 grams) egg yolks, at room temperatur
  
• ¾ cups (149 grams) granulated sugar, divided
  
• 3 large (106 grams) egg whites, at room temperature
  
• ¼ teaspoons cream of tartar
  
• ½ teaspoons vanilla extract
  
• Confectioners’ sugar, for dusting
  

• Blueberry cream
• 1½ cups (352 grams) cold heavy cream
  
• 2 tablespoons confectioners’ sugar
  
• ½ cups (170 grams) blueberry jam
  
• 1 teaspoon vanilla extract
  
• Confectioners’ sugar, for finishing