This is a picture of the chocolate cake I have made, after slicing and freezing. You will notice that there are a lot of air holes in the layers.
Is it a case of too much leavening? I mixed the batter with a hand whisk and i stop mixing when both dry and wet ingredients are fully mixed.
This is the recipe I use for 3 layers of 6" cake. 200 grams batter per layer. I use to bake it layer by layer in 3 separate pans but I found that baking 2 layers (400 grams batter) in one pan gives the cake more rise before it domes. I then torte it into 2 layers.
104 grams All Purpose Flour
38 grams Dutch-Processed Cocoa Powder
1 teaspoon Baking Powder
1 teaspoon Baking Soda
0.5 teaspoon Salt
150 grams Caster Sugar
1 large Egg
1 large Egg Yolk
50ml Vegetable Oil
87ml Hot Coffee
I use a ratio of 9:1 whole milk:vinegar to make buttermilk. I mix all the dry ingredients together after sifting the flour, cocoa powder and leavening agents. Then add all the wet ingredients except hot coffee, whisk to mix egg in then add hot coffee last (to avoid cooking the eggs if I add them all together).
When baking 2 layers in a pan, the air bubbles in the bottom later (after slicing) are smaller than the ones on the upper layer. When baking 1 layer at a time, the cake domes way too fast, usable cake layer is very short in height and air bubbles are huge.
Any advice will be greatly appreciated!
Too much baking soda, I guess too much baking powder, depending on how you look at it. Baking powder plus baking soda generally are not the same amount when using both together.
A lot of tunneling can be a sign of a too hot oven as well.
1.8 (150 C) + 32 = 302 F
If that's an accurate reading, that shouldn't be too hot for baking.
With that in check, you might look to the leavening, but usually an over-leavened cake will collapse in the center somewhat near the end of baking because the structure is weakened.
Is this a one time occurrence with this recipe, or is it consistently happening? If so, maybe you might want to look at another recipe.