Preheat oven to 350 degrees F. Line a standard muffin pan with paper liners.: As the oven warms, you will notice a faint, dry heat that promises golden edges. Preheating is crucial for even rise, because inserting batter into a cold oven produces flat cakes. A good test is to place a thermometer near the center to confirm the temperature. Common mistake, skipping preheat or underestimating the oven time leads to uneven tops and dense centers, so never rush this step.
In a medium bowl, whisk together the flour, baking powder, salt, cinnamon and ginger; set aside.: The dry mixture should look uniform with tiny specks of spice throughout. Whisking aerates the flour slightly and evenly distributes the leavening, which creates consistent lift. If you see clumps, press them through a fine sieve. People often forget to whisk dry ingredients which can create pockets of baking powder and uneven flavor.
Using an electric mixer on medium speed, beat the butter until soft and creamy, about 2 minutes. Add the granulated sugar and beat until light and fluffy, about 2 minutes, stopping to scrape the bowl as needed. Add the egg and vanilla extract and beat until completely combined, about 1 minute.: You will notice the butter change from dull and stiff to pale and ribbon like, and the sugar incorporation gives the mixture a slightly airy texture. Scraping the bowl prevents pockets of unincorporated butter or egg. Overbeating after adding the egg can create a batter that collapses, so stop as soon as it looks homogeneous.
Reduce the mixer speed to low and beat in half of the flour mixture until mostly combined, then pour in the buttermilk (the mixture may begin to look curdled - that's okay), then add the remaining flour mixture, mixing until just barely combined. Using a rubber spatula, scrape down the sides and bottom of the bowl and fold in the shredded apple, as well as any accumulated juices.: The batter will look slightly lumpy and a little curdled when the buttermilk hits it, which is fine because it indicates chemical interaction with the leavening. Folding preserves the air you built in the creaming step and keeps the cupcakes tender. When you fold in the shredded Gala apples , notice the flecks of fruit distributed through the batter. A common mistake is overmixing here which makes the cupcakes tough, so fold until you no longer see streaks of flour.
Divide the batter between the 12 muffin cups and bake until a toothpick inserted in the center comes out clean, 20 to 25 minutes. Remove from the oven and cool for 5 minutes, then remove the cupcakes from the pan and place on a wire rack to cool completely.: As they bake you will smell a warm spice and the tops will turn a light golden brown with slightly domed crowns. The toothpick test is your best indicator of doneness, and a little moist crumb on the pick is fine. Letting them cool in the pan for too long can trap steam and make the bottoms soggy, so transfer to a wire rack after a brief rest.
Make the Frosting: With an electric mixer on medium-high speed, beat the butter until fluffy, 2 to 3 minutes. Add the cream cheese, vanilla and salt and continue to beat for an additional 2 minutes, scraping the sides of the bowl as needed. Reduce the mixer speed to low and add the powdered sugar gradually and mix until smooth and combined, scraping down sides of bowl as needed. Add the ground cinnamon, mix until it is incorporated, then increase the mixer speed to medium-high and beat until light and fluffy, 1 to 2 minutes.: With an electric mixer on medium-high speed, beat the butter until fluffy, 2 to 3 minutes. Add the cream cheese, vanilla and salt and continue to beat for an additional 2 minutes, scraping the sides of the bowl as needed. Reduce the mixer speed to low and add the powdered sugar gradually and mix until smooth and combined, scraping down sides of bowl as needed. Add the ground cinnamon, mix until it is incorporated, then increase the mixer speed to medium-high and beat until light and fluffy, 1 to 2 minutes. : The frosting should become glossy and cloud like, with a gentle lift as air is incorporated. The scent will be creamy with a hint of cinnamon . Adding the powdered sugar slowly avoids a gritty texture and ensures a silky mouthfeel. If the frosting is too soft, chill briefly; if too stiff, add a teaspoon of milk. A mistake I see often is adding all the sugar at once which makes the bowl puff cloud and creates a mess or grainy frosting.
Using a decorating bag and tip (I used the Ateco #827 tip) or an offset spatula, frost the tops of the cupcakes. The cupcakes can stay at room temperature for a few hours, but should be refrigerated in an airtight container for longer-term storage up to 4 days. Bring the cupcakes to room temperature before serving.: Piping produces a neat, swirled crown that showcases the frosting texture and retains moisture. If you prefer, you can spread the frosting with an offset spatula for a rustic look. For storage the cold container keeps the cream cheese stable, and returning to room temperature restores that spreadable, creamy sensation. A common error is leaving frosted cupcakes out too long in warm conditions which softens the frosting and can break down the structure.
