Finishing and decoration rely on several foundational frostings and icings. Buttercream is a broad category: American buttercream mixes butter with powdered sugar for a very sweet, easy-to-make frosting; Swiss meringue buttercream heats egg whites and sugar to 160°F, whips them to stiff peaks, then adds butter, producing a silkier, less sweet, more stable frosting ideal for professional finishes. Ganache is simply chocolate and cream heated until smooth, with ratios determining use—1:1 for a pourable glaze, 2:1 chocolate to cream for truffles or thick frosting, 1:2 for a thin sauce. Royal icing combines powdered sugar, egg whites (or meringue powder), and lemon juice, drying hard and smooth for cookie decorating and gingerbread houses. Fondant is a smooth sugar paste that can be rolled out and draped over cakes for a flawless finish or heated and poured over pastries like petit fours. A crumb coat—a thin initial layer of frosting sealed by refrigeration—traps loose crumbs so the final coat goes on clean.
Precision matters in baking because it is a science of ratios. Weighing ingredients on a scale accurate to 1 gram ensures consistency: a cup of flour can vary from 120 to 180 grams depending on how it is measured. Baker's percentage (expressing each ingredient as a percentage of total flour weight) and conversion to grams before scaling simplify recipe adjustments, though leavening and spices may not scale perfectly in very large batches. The toothpick test offers a quick doneness check—insert a toothpick into the center of a cake; if it comes out clean or with a few moist crumbs, the cake is done, while brownies with a few moist crumbs are fudgy and clean-toothpick brownies are cakey.
Common baking problems usually trace back to specific causes. Cakes sink in the middle when there is too much leavening, the oven door is opened too early, the cake is underbaked, or there is too much sugar or liquid. Muffin tunnels form when batter is over-mixed, allowing gluten strands to develop channels that steam follows during baking. Cookies spread too much when butter is too warm, there is too much sugar or baking soda, the oven is too cool, or dough is placed on a hot baking sheet. Cheesecake cracks from over-baking, rapid temperature changes, or over-mixing that incorporates too much air—using a water bath, avoiding oven door opening, and letting the cake cool gradually in the turned-off oven all help.
Macaron shells crack from under-mixing the batter, an oven that is too hot, or insufficient resting before baking; proper macaronage—pressing and folding the batter until it flows like lava and a ribbon sinks back into itself in about 10 seconds—and resting piped shells until dry to the touch help prevent cracking. At high altitude, lower air pressure causes faster rising and quicker evaporation, so bakers typically reduce leavening by 25%, increase oven temperature by 15–25°F, slightly increase liquid, and slightly reduce sugar while increasing flour.