Preheat the oven to 400°F. Lightly spray 20 muffin cups with nonstick spray.: You will notice the oven warming and a dry, hot air filling the cavity, which primes the baking environment for immediate lift. Preheating ensures the baking powder reacts properly, creating domed tops and a gentle crumb. A common mistake is to skip full preheating, which can yield flat, dense muffins. If your oven runs hot, use an oven thermometer to check accuracy and avoid overbrowning.
In a large mixing bowl, whisk together the flour, sugar, baking powder, salt, baking soda and allspice. Make a well in the center.: As you whisk the dry mix, you will hear the dry powdery sound and see a uniform pale mixture with specks of spice. Creating a well helps combine wet and dry ingredients without overworking the gluten. Overmixing here is a typical error, it tightens the gluten and leads to tough muffins, so keep the dry blend light and airy before adding the wet mix.
In a separate bowl, combine the sour cream, oil and eggs; stir in the peaches. Pour the peach mixture into the well. Stir just until moist (don’t over-mix). Batter should be lumpy.: The wet bowl will look glossy and slightly thick from the sour cream . As you stir, the mixture becomes smooth, and when you fold in the chopped peaches you will see juicy flecks suspended in the batter. This combination adds moisture and fat that keep the crumb tender. A pitfall here is overmixing the fruit into the wet base until it breaks down, which can release too much liquid and weight down the batter.
Spoon the batter into the prepared muffin cups, filling 2/3 full. Bake 20 to 25 minutes.: When you add the wet mix to the dry well, you will notice the batter beginning to come together around the edges first. The contrast of powdery flour and glossy wet mix is tactile and tells you when to stop. This 'well' technique prevents vigorous mixing, which is crucial because vigorous mixing develops gluten that makes muffins chewy rather than soft. If the batter looks uniform immediately, you may have overmixed earlier, so fold gently from now on.
Stir just until moist (don’t over-mix). Batter should be lumpy.: The batter should feel slightly thick and cling to your spatula, with small lumps visible, and you may hear a soft scraping sound as you fold. These lumps mean you have not overworked the gluten, preserving a tender crumb. The aroma of brown sugar and allspice will be faint but present. Overmixing here flattens the muffins and produces a dense texture, so stop when streaks of flour are mostly gone.
Spoon the batter into the prepared muffin cups, filling 2/3 full. Bake 20 to 25 minutes.: As you fill the cups, you will see dome shapes form while baking and smell warm caramel notes from the brown sugar . The muffins will rise and the tops will turn a golden color with slight crackling. For doneness, a toothpick inserted in the center should come out with a few moist crumbs, not wet batter. A common error is opening the oven repeatedly during baking, which drops the temperature and can prevent proper rise, so avoid unnecessary peeks.
