Imagine enjoying a fresh-from-the-oven corn muffin with your morning coffee... at home... on a Tuesday... without mixing a single ingredient. How is that possible? The answer lies in a muffin batter that you can make on the weekend and keep in the refrigerator for up to a week. Then, whenever you're craving a muffin for breakfast or for an afternoon snack with tea, all you have to do is scoop some batter into a tin and bake.
At the Downtown Bakery, we make lots of delicious breakfast pastries every morning. But even for us, making batters from scratch every day is time-consuming. I began wondering how we could make larger batches less frequently. Ideally, I wanted to make the batters at the beginning of the week when we're less busy. Then, as the crowds thicken at the end of the week, we'd only have to bake the muffins.
The right amount of leavening is key
We were already making rich chocolate brownie-style muffins from a batter that's made ahead, refrigerated, and then scooped and baked daily, so I knew the concept was feasible. But when I first tried refrigerating my other muffin batters (including cornmeal-cherry muffins and pumpkin-spice muffins), I wasn't successful. After a few days in the fridge, the batter would become too liquid to scoop, and the muffins would come out flat and heavy. Why didn't these batters work as wonderfully as the chocolate muffins? I realized that the biggest problem was the chemical leaveners -- the baking powder and baking soda -- in the other batters. (The chocolate muffin has no chemical leaveners.) So I focused my experiments on the leaveners.
Leaveners give muffins lift and keep them tender. Eliminating the leaveners for these muffins was never an option. The leaveners in muffins and other baked goods make them light and tender and give them lift. (Because the chocolate muffin is denser--more brownie-like than muffin-like -- it works well using eggs alone as the leavener.) Getting the correct ratio of leavening seemed to be the trick to creating a batter that would store well.
Chemical leaveners work by reacting with acids to create carbon dioxide, the same gas that yeast produces. Baking soda begins to create gas when moistened. Double-acting baking powder (which most baking powders are these days) produces an initial set of gas bubbles when mixed with wet ingredients and then a second set when heated. The first reaction forms many small gas cells in the batter; the second reaction expands the bubbles to create a light texture.
The problem with trying to store a batter that contains baking soda or baking powder is that the leavening agents continue to produce gas bubbles until they're used up. Over time, those bubbles will collapse, resulting in dense muffins with little loft.
Adding more leavening helps -- as long as it isn't too much. What seemed to work best was to add a little baking soda to recipes that had only called for baking powder, but I had to be careful not to add too much. A funny thing happens with chemical leaveners. Food scientist Shirley Corriher describes it this way: with too much leavening, the gas bubbles get too big, they run into each other, float to the top of the batter, and escape.
Once I added baking soda, I had to consider that it can leave a soapy taste behind. So in each recipe, I neutralized that soapy quality with acidic ingredients such as sour cream, buttermilk, yogurt, or lemon juice. The added acid seemed to improve the batter's shelf life. I also cut back on the liquid ingredients so that the chilled batter wouldn't liquefy over time.
Overmixing will pop the gas bubbles produced by the leaveners, resulting in flat muffins. Any lumps will disappear during baking.
Careful mixing and quick chilling also benefit the batter. Being careful not to overmix the batter (any lumps will disappear during baking) is even more essential in these muffin batters than most. Overmixing toughens the batter and also encourages the dissipation of the carbon dioxide.
Getting the batter into the fridge as quickly as possible will also give it better staying power. The initial reaction in baking powder occurs at room temperature; chilling the batter quickly will slow that initial reaction, allowing more gas bubbles to be created slowly over time.
With the basic batter established, you can tinker with the flavorings. As I experimented with the leavening for the pumpkin and cornmeal muffins, I also played with the flavorings. You can substitute just about any fruit purée -- apple, peach, pear, apricot, banana, sweet potato -- for the pumpkin. And the cornmeal muffins are wonderful with fresh blueberries in place of the cherries. You could also make the corn muffins savory by cutting back on the sugar and lemon and by adding corn kernels and jalapeños in place of the cherries.