Step 1

Start with baking the sponge cake. Preheat the oven to 356°F.

Step 2

Bring the eggs to the room temperature by putting them inside the bowl with warm water. Keep them there for 5 minutes. If the eggs are already warm, go to the next step.

Step 3

Mix the flour, potato starch, and baking powder in the bowl. Sift the mixture to make sure there are no lumps.

Step 4

Separate whites from egg yolks.

Step 5

Whip egg whites until they make a solid foam.

Step 6

Start adding sugar slowly, mixing all the time.

Step 7

Add egg yolks, one by one, mixing all the time.

Step 8

Using the slowest speed of mixer or a spoon, start adding the flour mixture. Make sure you do it slowly and gently.

Step 9

Place the dough in the 9x13" pan and bake for 35-40 minutes.

Step 10

Mix the strawberry gelatin with 3 cups of boiling water and wait until it cools off.

Step 11

Now it's time to make the custard. If you want to see step-by-step photos of how to make it, follow this link.

Step 12

Pour about half a cup of milk to the small bowl and the rest to the pot.

Step 13

Add egg yolks and sugar to the pot., Whip it together until you get a smooth, yellow color. Start cooking slowly, stirring as often as possible.

Step 14

Add flour and potato starch to the milk in the bowl. Mix until dissolved.

Step 15

When the mixture in the pot nearly boils, add the milk with the flour from the bowl.

Step 16

Stir until you will get the consistency of the pudding. Cool off.

Step 17

When the pudding is cold, mix it with butter to get a smooth custard.

Step 18

Cut the cold sponge cake in half (horizontally).

Step 19

Spread the custard (about 2/3 of the entire portion) on the first half. Add cut in half strawberries.

Step 20

Cover it with the second half of the sponge cake.

Step 21

Spread with the remaining custard. Add cut in half strawberries.

Step 22

Pour the solidifying jelly on the cake and place it in the fridge. Wait for 2-3 hours until it's cold and ready to eat.