Preheat the oven to 375°F (190°C). Grease a 12-cup muffin pan with butter or spray with non-stick cooking spray.: When you start, the warm rush of oven heat becomes part of the ritual, and that preheated environment ensures the batter begins rising immediately. You should smell a faint toasty scent the moment the oven reaches temperature, which signals a steady, even bake. Greasing the pan helps release the muffins cleanly, preserving their tops. A common mistake is skipping greasing, which can make those beautiful domes stick to the pan, tearing when removed.
In the bowl of an electric mixer, beat together the butter, granulated sugar and brown sugar until fluffy, 1 to 2 minutes. Scrape down the sides of the bowl with a rubber spatula.: As you cream butter and sugars, watch the mixture lighten in color and increase in volume, creating tiny air pockets that will help the muffins rise. The sound of the mixer will change from a heavy whir to a lighter, aerated tone, and the texture should look creamy. Scraping the bowl prevents unmixed pockets, so every bite has balanced sweetness. Overworking the mix is a trap, it can melt the butter and reduce lift, so stop once it looks light and uniform.
Add the egg and mix well, stopping to scrape the bowl if necessary.: Adding the egg incorporates structure and moisture. You will notice the batter become smoother and slightly more cohesive. The glossy appearance of the batter indicates good integration. If you add the egg to cold butter, it may not emulsify properly, so ensure the butter is at room temperature to prevent a separated, curdled mix.
Beat in the yogurt. The batter will look a little curdled—that's okay.: When you fold in yogurt , the batter might appear slightly curdled but this is normal, due to the dairy interacting with the beaten fats. The tang of the yogurt enhances flavor while keeping the crumb moist. The batter should still be cohesive enough to hold chopped apple . If it seems too thin, a short rest lets the flours hydrate and thicken without overmixing.
Add the flours, baking powder, baking soda, salt, cinnamon, nutmeg and cloves. Beat on low speed until just combined. The batter will be very thick.: As you add dry ingredients, they will dull the sheen and thicken the batter noticeably. The smell of cinnamon will become prominent, releasing warm aromas. Low speed prevents gluten overdevelopment, which keeps the muffins tender. Overmixing here leads to tough muffins with tunnels, so stop as soon as you no longer see loose flour.
Add the chopped apples and mix until just combined. Do not over-mix.: Folding in the chopped apples introduces pockets of moisture and little bursts of fruit in every bite. The batter will look chunky and uneven, which is what you want; these visual cues mean the fruit is distributed but not pulverized. Overmixing could break down the pieces and yield a gummy texture, so fold gently until you see even specks of apple throughout.
Use an ice-cream scooper or large spoon to divide the batter evenly among the prepared muffin cups. The cups should be full. Sprinkle the 6 tablespoons of brown sugar evenly over top.: Filling the cups generously encourages a nice domed top and a moist interior. The scoop provides uniform portions so baking is even across the pan. When you sprinkle the extra dark brown sugar , it creates a sweet, caramelized crown that crackles a little in the oven, adding contrast. Avoid underfilling, which produces flat muffins, or overfilling, which can lead to spillover.
Bake the muffins for 25 to 30 minutes, or until a toothpick inserted into the center of a muffin comes out clean.: During baking, your kitchen will fill with a warm, spiced perfume, and the tops will turn golden brown with slightly crisp edges. Listen for a faint set sound when you tap the top, and check the centers near the lower end of the time. A clean toothpick indicates set crumb without wet batter. A common mistake is removing muffins too early, leaving them gummy in the center; always test before pulling them from the oven.
Remove the muffins from the oven, cool them for 5 minutes in the pan, then turn them out onto a rack to finish cooling completely.: Letting them rest in the pan allows steam to settle and the structure to firm up; you will see the tops slightly contract as they cool. Turning them onto a rack prevents condensation from making bottoms soggy. If you skip the short cool in the pan, the muffins may collapse or stick, so give them those precious minutes.
Freezer-Friendly Instructions: The muffins can be frozen in an airtight container or sealable plastic bag for up to 3 months. Thaw for 3 to 4 hours on the countertop before serving. To reheat, wrap individual muffins in aluminum foil and place in a preheated 350°F (175°C) oven until warm.: The muffins can be frozen in an airtight container or sealable plastic bag for up to 3 months. Thaw for 3 to 4 hours on the countertop before serving. To reheat, wrap individual muffins in aluminum foil and place in a preheated 350°F (175°C) oven until warm. : Frozen muffins keep their texture well, and the reheating step brings back a just-baked warmth and renewed aroma of cinnamon and apple . Thawing on the counter preserves moisture, and a short oven warm-up restores a pleasant exterior chew. Avoid microwaving from frozen without a cover, it can dry them out and make the crumb rubbery.