Technically speaking, infusing flavor into a cupcake involves steeping a flavorful substance in liquid and using the liquid in the batter, filling or topping. Sometimes infusion is necessary to achieve a certain flavor profile, but the modern baking cupboard includes flavor extracts, which provide a convenient alternative and also give good results. If you have the time, infusions allow exotic and unusual flavor combinations.
Vanilla extract is nearly ubiquitous in baked goods, and most cupcake recipes will call for a teaspoon or two. To infuse vanilla flavor into cupcakes instead of using extract, slice open half a dried vanilla bean lengthwise and scrape out the seeds. Place the seeds and the bean in the liquid component of the recipe -- usually milk -- and heat the mixture until just steaming. Remove it from heat, cover it, let it cool, remove the bean and proceed with the recipe. Vanilla bean infusions yield delicious, distinctively brown-speckled cakes.
Tea and Coffee
Tea-flavored cupcakes are a trendy treat, and the infusion process is similar to making a cup of tea. Heat the liquid component of the batter to just boiling and add about 4 teabags or 2 tablespoons loose tea per dozen cupcakes. Cover the liquid and remove it from the heat. Let it steep for 10 minutes, then remove the teabags or strain the liquid. Flavored teas, such as chai and Earl Gray, work especially well. For coffee infusions, use freshly ground coffee or replace the liquid in the recipe with strong brewed coffee. For green-tea-flavored cupcakes, add powdered green tea, called matcha, directly to your batter.
Citrus and Aromatics
To infuse citrus flavors, use a zester to remove strips of zest from a lemon, orange or other citrus fruit. Submerge the zest in the simmering liquid component of the recipe, remove from heat, cover, cool and strain. You can do the same with chunks of fresh ginger, cinnamon sticks, cardamom pods or peppercorns. Infusions of this sort are most useful when you want to add flavor with no tiny pieces or zest or spice in the batter. Otherwise, adding finely grated citrus zest, ginger or powdered spices directly to the cupcake batter works as well.
Spirits and Beers
A small amount of liquor can add a punch of flavor to cupcakes. For rum raisin cupcakes, for instance, soak raisins in rum, and add a spoonful of rum to the batter. Next, layer on even more flavor with rum glaze and rum frosting. Kirsch -- cherry brandy -- adds sophisticated fruit flavor to vanilla or chocolate cupcakes. Dark beers, such as stouts and porters, lend interesting dimensions to chocolate and gingerbread. Replace some or all of the liquid component of the recipe with your beer of choice.
Granulated white sugar has a neutral taste, but just a spoonful or two of others sweeteners will add distinctive flavors. Tangy, rich molasses enlivens ginger, spice or chocolate cupcakes. Maple syrup adds caramel and herb notes and combines well with nuts. It's a terrific flavoring for glazes and frosting. Substitute maple extract if the real thing is too pricey. Brown rice syrup and brown sugar both add subtle caramel undertones. Use caution when replacing white sugar with other sweeteners, as this can change the texture of the cake.
The flower infusions rosewater and orange flower water are staples of Middle Eastern pastry making and widely available, inexpensive and excellent. Both make lovely flavorings for cupcakes and cupcake glazes. Another common way to infuse cupcakes with flavor is to glaze them with infused simple syrup. Combine water, sugar and the flavoring agent in a saucepan and gently simmer the mixture until the sugar dissolves. Let it cool, and store the syrup with the flavoring agent for intense flavor. Citrus peel, ginger, lavender, rosemary and other herbs all make interesting and delicious cupcake glazes.