01 -
In a small mixing bowl, combine flour, cold butter cubes, both sugars, salt, and cinnamon. Cut the butter into the flour using your fingers until you have small pea-sized pieces of streusel.
02 -
Stir in the reserved diced apples. Refrigerate the streusel topping until ready to use.
03 -
Preheat oven to 425°F (220°C) and adjust oven rack to the middle position. Line a muffin pan with 4 muffin liners.
04 -
In a medium mixing bowl, combine sour cream, pumpkin, juice, both sugars, egg yolk, and vanilla extract. Mix with a fork until smooth. Stir in the apple cubes.
05 -
In a small mixing bowl, whisk together flour, baking soda, salt, and pumpkin pie spice. Sprinkle these dry ingredients over the wet ingredients.
06 -
Use a spatula to fold the dry ingredients into the batter until no dry streaks remain. Do not overmix to avoid chewy muffins.
07 -
Evenly distribute the batter among the prepared muffin liners. Top each muffin with equal portions of the streusel topping.
08 -
Bake at 425°F (220°C) for 5 minutes to help muffin tops rise. Then reduce heat to 350°F (175°C) and bake for an additional 11-13 minutes, or until a toothpick inserted in the center comes out mostly clean.
09 -
Cool the muffins in the pan on a wire cooling rack for 10 minutes, then transfer the muffins directly to the rack to cool completely. Store covered at room temperature for 3-5 days.