Chocolate sponge cake batter being poured into pan
The Rule To Follow For Filling Baking Pans With Batter
If you’re unsure of how much batter you should add to a baking pan, there’s a helpful rule to follow. For thick batters that won't rise too dramatically, 2/3 full is your best bet.
These thick and heavy batters include those for pound cakes, butter cakes, and quick breads, where sugar-butter creaming or chemical leaveners are used to give the cake lift.
For cakes that are aerated with meringue or an egg foam, like chiffon or sponge cakes, 1/2 full is the way to go. The foamy bubbles in the batter will help it rise twice as tall.
If you’re not sure where your cake lands on the light-to-heavy scale, go with the safer 1/2 full method. If you have leftover batter, pop it in a mini-loaf pan or a muffin tin.