Loaf Pan Chocolate Castella Cake

Ingredients

4 eggs
60g granulated sugar
65g cake flour
10g cocoa powder
10g chocolate chips
40g vegetable oil 
95g milk 

6g lemon juice 
6g vanilla extract 
60g chocolate chips chopped and shredded

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

Steps:

1. Separate 4 eggs. Keep the egg white bowl cool in the fridge.
2. Heat the vegetable oil to 158℉(70℃). Pour the oil into a dry and clean bowl.
3. In a clean bowl, add cake flour, cocoa powder and 10g chocolate chips into the heated oil, mix until well combined. Add in milk, mix until smooth. Add in 4 egg yolks and mix well. Set aside.
4. Preheat the oven to 140℃/284℉.
5. Add lemon juice, granulated sugar and vanilla extract into the egg white, use a hand mixer to beat until it forms soft peaks.
6. 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.
7. Line the loaf pan with parchment paper. Pour in half of the batter, sprinkle some shredded chocolate in the middle, and pour in rest of the batter, Smooth it out.
8. Pour some hot water (about 1-2 cm high) into the baking sheet, top it with a wire rack, and place the loaf pan on it. Let bake for 60-65 minutes.
9. Once the cake is fully cooked, take it out of the oven, take the cake out of the loaf pan and let it cool down on the cooking rack. Or the cake may get too moist.