Old-Fashioned Coffee Cake

Why This Old-Fashioned Coffee Cake Works

During mixing, the softened butter and sugar trap a lot of tiny air pockets as they are beaten together. Those little pockets stay in the batter when the eggs and vanilla go in, so the cake starts out light even before it hits the oven. When the flour, baking powder, and baking soda are added, they give the batter enough structure so it can rise around those air pockets instead of collapsing.

As the cake bakes, the sour cream keeps the batter thick and moist. It loosens the dough just enough so it spreads in the pan, but it also keeps the crumb soft instead of dry. The baking powder and baking soda react in the warm, slightly tangy batter and push the cake up, while the eggs set and hold everything in place.

On top, the cold butter is rubbed into the brown sugar, flour, and cinnamon, so it stays in little bits. In the oven those bits slowly melt, the sugar firms up, and the topping sets into a crisp, crumbly layer that contrasts with the soft cake underneath.

Mistakes To Avoid

Overbaking this cake easily dries it out. Once it goes past the 40-minute mark, the edges start to harden and the crumb topping can turn from crisp to hard and slightly burnt, while the inside loses its soft, tender texture and becomes crumbly.

Creaming the butter and sugar too little leaves the mixture dense and grainy. Without enough air beaten in at this stage, the cake doesn’t rise well in the oven and comes out flat and heavy instead of light and soft.

Overmixing the batter after adding the flour and sour cream makes the cake tough. The more the batter is worked at this point, the tighter the crumb becomes, so the finished cake slices feel chewy instead of moist and delicate.

Using warm or soft butter in the crumb topping causes it to smear into a paste instead of forming loose crumbs. In the oven this melts into a thin, greasy layer, so the top of the cake bakes up patchy and lacks that chunky, crunchy streusel.