Classic Madeleines

• 2 tablespoons softened butter (for brushing the molds), plus 1 stick (¼ pound [115 g]) unsalt

Brush 2 madeleine molds (assuming your molds make 12 madeleines each) with softened butter and slide the molds into the refrigerator. After about 15 minutes, brush them again, making sure you brush the butter around the indentations on top—otherwise, as the madeleines expand, they may stick to the top of the mold. Refrigerate again for at least 15 minutes.

Grate the zest off half the le