This is the chocolate cake I baked:
Notice the dark layer at the bottom. I followed this recipe (used only half of all ingredients, since the recipe is for making batter that fills two 9 inch pans). The vegetable oil I used was refined sunflower oil. I whisked the batter manually with a whisk, for less than 2 minutes. The 22L oven was pre-heated for around 7 minutes. I poured the batter into the pan, slammed it on the kitchen counter a few times to get rid of bubbles and placed it in the oven.
Since the cake shown on the page that hosts the recipe does not have a separate dark layer at the bottom, I'm assuming I did something wrong with the cake I baked. On eating it, it tastes delicious and appears to be fully baked.
Does such a layer form due to inadequate whisking? Is it primarily the oil or egg that has settled to the bottom, and is it because the batter is runny? How do I get it to be uniform?
Surprising detail: The piece of cake kept on top, does not have the dense layer for an inch along the left edge. Also, the dense layer seems to increase in height as it reaches the middle of the cake.
Extra info in response to comments:
This is a standard sponge cake I baked 2 months ago (my first attempt at baking a cake). Used parchment paper lining (the paper jutted into the cake, which is why you see a crevice at the side). Had whisked the egg whites for a long time with an electric mixer. The baking powder and baking soda are old. I do believe the upper and lower heating elements of the oven work fine. For both cakes, I poured the batter into an aluminium pan, placed the pan onto the baking tray provided with the oven, and inserted the baking tray into the center slot of the oven, with the top and bottom heating elements active. Now I noticed that many people keep the pan on a metal mesh/rack, and I wonder if my mistake was in using the baking tray instead of the metal rack which might've done a better job in transferring heat to the bottom of the pan.
Chocolate cake recipe used:
For anyone who isn't able to access the website.
- 2 cups sugar
- 1.75 cups all-purpose flour
- 0.75 cup Hershey's Cocoa
- 1.5 tsps baking powder
- 1.5 tsps baking soda
- 1 tsp salt
- 2 eggs
- 1 cup milk
- 0.5 cup vegetable oil
- 2 tsps vanilla extract
- 1 cup boiling water
- Heat oven to 350°F (177°C). Grease and flour two 9-inch round baking pans.
- Stir together sugar, flour, cocoa, baking powder, baking soda and salt in large bowl. Add eggs, milk, oil and vanilla; beat on medium speed of mixer 2 minutes. Stir in boiling water (batter will be thin). Pour batter into prepared pans.
- Bake 30 to 35 minutes or until wooden pick inserted in center comes out clean. Cool 10 minutes; remove from pans to wire racks. Cool completely. Frost with "Perfectly Chocolate" Chocolate Frosting.
Used an electric mixer to beat the batter and baked the cake again. Waited till the thermostat switched off and waited a bit more before putting the pan in. (I made a mistake with the first chocolate cake. The aroma of chocolate batter being baked, is similar to a burning smell. Also, one of the reviews of the recipe says that the cake exploded. So due to the smell, and when I saw 4 large bubbles forming at the top of the cake 10 minutes into baking, I had lowered the temperature to less than 175°C for a while). But this time I kept the temperature steady throughout, and here's the result. I added a butter + milk powder + water + sugar + vanilla ganache, because I forgot to add vanilla to the batter. It seems like the ganache has penetrated 1cm into the cake.
Observation 1: The baking powder used for all these 3 cakes, has a manufacturing date of July 2013 (best before 24 months from manufacturing date). The baking soda was made in August 2020 (best before 20 months from manufacturing date). So expired baking soda/powder wasn't the issue.
Observation 2: As one keen person observed and mentioned in a now-deleted comment, the first chocolate cake had risen and sunk. Also, as noted in the "surprising detail" above, even at the bottom layer, one inch is properly baked toward the edge. So I'm inclined to believe the problem was with heating. Especially since the layer increases in height toward the center.
Observation 3: As rumtscho mentioned, the problem could also be due to inadequate mixing. The large bubbles that formed during the first chocolate cake baking, were also a result of inadequate mixing. I'll try some experiments in the next few months to confirm.
Observation 4: Heat transfer to the bottom of the pan is fine when the pan is placed on a baking tray. No explicit need to place it on a metal rack.
Like the first time, I whisked the batter using a whisk for 2 minutes instead of using an electric mixer. This time, I waited until the oven was heated properly, before putting the pan in, and I maintained the temperature at 180 throughout. It didn't form the layer at the bottom.
Conclusion: It was the lowering of the temperature in-between, and the fact that I didn't wait until the oven got hot before putting the pan in, that caused the layer to form. However, comparing with the texture of the cake in experiment 1, it's necessary to use an electric mixer to get a cake that's well-blended and well-risen.