Passover Citrus Sponge Roll

Ingredients

 * 4 eggs
 * 1 yolk
 * ¾ cup superfine sugar
 * 1 lemon, juice and zest
 * ½ cup sifted potato starch
 * 1 pinch salt
 * ¾ cup sugar
 * 3 tbsp potato starch
 * ¾ cup orange juice
 * 1 tbsp lemon juice
 * 3 egg yolks
 * 2 tbsp margarine

Sponge roll

 * 1) Preheat oven to 350°F.
 * 2) Beat egg whites until stiff, adding half the sugar gradually; set aside.
 * 3) Using the same beater, beat the yolks while adding the remaining sugar, until mixture is very light.
 * 4) Stir lemon juice, rind, potato starch and salt into yolks.
 * 5) Gently fold in whites, starting with a quarter of the mixture, then adding the rest.
 * 6) Gently spread onto a cookie sheet lined with parchment paper and lightly sprayed with non-stick vegetable oil spray.
 * 7) Gently smooth the surface.
 * 8) Bake for 10 – 15 minutes or until sponge has risen slightly and is lightly browned.
 * 9) Remove from oven and turn cake out onto a clean cloth.
 * 10) Allow to cool.
 * 11) Spread orange filling evenly over cake and gently roll up using cloth to help lift cake.
 * 12) Sprinkle with sugar and/or whipped cream - etc.

Orange filling

 * 1) Combine sugar, potato starch, orange juice and lemon juice in a saucepan and bring to a boil.
 * 2) Boil 1 minute, while stirring constantly.
 * 3) Remove from heat.
 * 4) In a separate bowl, beat egg yolks.
 * 5) Stir a little bit of orange mixture into egg yolks then add yolks to the sauce pan.
 * 6) Cook gently for one minute.
 * 7) Stir in 2 tablespoons margarine, allow mixture to cool before using.