Chocolate Castella Cake

INGREDIENTS YOU WILL NEED

• 95g vegetable oil
• 100g cake flour
• 18g cocoa powder
• 25g dark chocolate
• 8 eggs
• 100g milk
• 95g granulated sugar
• 8g lemon juice
• 8g vanilla extract

Notes: By cake flour, I mean low protein flour, which normally contains 7-9% protein (Mine is around 8%). Not self-rising flour.

HOW TO MAKE CHOCOLATE CASTELLA CAKE

1. Preheat the oven to 302℉(150℃). Separate the eggs. Keep the egg white bowl in the fridge.

Notes:

• The bowl to hold the egg white should be dry and clean. Make sure there is no water drops left or any signs of grease.
• There should be no egg yolk segments mix in the egg white, however small the segment may be. You can separate eggs one at a time over a small bowl, make sure the egg yolk is not broken and not mix with the egg white, then pour the egg white into the final egg white bowl and then continues with next egg.
• Once done separating the eggs, keep the egg white bowl cold in the fridge, which will help you whip up the egg white.
• Wait until you done making the batter, then you whip up the egg white.

2. Heat the vegetable oil to 158℉(70℃).

Notes:

• If you do not have a thermometer, heat the oil over medium/low heat about 60 seconds. Do not overheat the oil.
• When you can see many tiny bubbles on the bottom of the pan, it means the oil is ready.
• Keep the heat low to avoid overheating the oil. If the oil is overheated, you will find the batter thicker than it should be after you add in the oil.

3. Transfer the heated oil to a clean bowl, add in cocoa powder and flour and mix well. Add in melted dark chocolate and milk and mix well. Add in egg yolks and mix well. Set aside.

Notes:

• You can sift all the dry ingredients to gain a fine texture.
• Mix ingredients in until just combined. Do not over mix them. When mix in dry ingredients, mix until you can see no dry bits left. Use a spatula to scrape the bottom a little to see if there is any dry ingredients left in the bottom of the bowl.

4. Add lemon juice, granulated sugar and vanilla extract into the egg white, use a hand mixer to beat until it forms soft peaks.

Notes:

• This recipe contains eggs. If you don’t like the smell of eggs, lemon juice and vanilla extract can help reduce the egg smell. The granulated sugar is to help whip up the egg white.
• Use a hand mixer to beat egg white on medium-high speed, until soft peaks form. This process should take several minutes. The right meringue texture should be shiny and smooth. And you will find it quite thick and feel resistance inside the whipped egg white when you moving the mixer around.

5. Take a scoop of whipped egg white to fold into the batter until just combined. Pour all the whipped egg white into the batter. Gently fold the whipped egg white into the batter until just combined.

Notes:

• Gently fold the whipped egg white in. Not whisking nor stirring. Use a spatula to gently “cut” in the whipped egg white until just combined.
• Do not stir in the egg white and do not over mix them. Or you may deflate the egg white, and then the cake will shrink.

6. Line the square springform pan (24*24*8cm) with parchment paper and pour all the batter into the pan. Smooth the surface. Give it a few taps (optional).

Notes:

• Gently smooth the surface.
• The taps are to get rid of the big bubbles for a finer inner texture. A few (one or two), not too much. If you are afraid of losing too many bubbles, just neglect this step.

7. Wrap the baking pan bottom with tinfoil to avoid water getting into the cake during water-bath baking. Pour some room temperature water (about 1 cm high)  into the baking sheet and place the springform cake pan into the baking sheet. Send into the oven to bake for 65 minutes.

Notes:

• Water bath. Pour water (about 1 cm high) into a baking tray. Preheat the oven with the baking tray and water in it. Wrap the springform pan with tinfoil before place it onto the baking tray. This way can avoid water getting into the springform pan. Especially when the pan you used has a removable bottom.
• A better way to avoid water getting into the pan is to place a cooling rack/wire rack onto the baking tray, and then place the springform pan onto the cooking rack. So the cake pan will not touch the water and the bottom of the cake will not easily get wet.
• Use a toothpick to dip into the cake, if the toothpick comes out clean, it means the cake is fully cooked. If not, extend the baking time.
• The cake will grow while baking, so it is important to leave some space for the cake to grow.

8. Once the cake is fully cooked, take it out of the oven, take the cake out of the springform pan and let it cool down on the cooking rack. Or the cake may get too moist.

Steps:

1. Preheat the oven to 302℉(150℃). Separate the eggs. Keep the egg white bowl in the fridge.
2. Heat the vegetable oil to 158℉(70℃). If you do not have a thermometer, heat the oil over medium/low heat about 60 seconds. Do not overheat the oil.
3. Transfer the heated oil to a clean bowl, add in cocoa powder and flour, and mix well. Add in melted dark chocolate and milk, and mix well. Add in egg yolks and mix well. Set aside.
4. Add lemon juice, granulated sugar and vanilla extract into the egg white, use a hand mixer to beat until it forms soft peaks. Take a scoop of whipped egg white to fold into the batter until just combined. Pour all the whipped egg white into the batter. Gently fold the whipped egg white into the batter until just combined.
5. Line the square springform pan (24*24*8cm) with parchment paper and pour all the batter into the pan. Smooth the surface. Give it a few taps. Wrap the baking pan bottom with tinfoil to avoid water getting into the cake during water-bath baking.
6. Pour some room temperature water into the baking sheet (about 1 cm high) and place the springform cake pan into the baking sheet. Send into the oven to bake for 65 minutes. Take the cake out of the can pan and let it cool down on the cooling rack.