In a medium bowl, combine 3 tablespoons of all-purpose flour, 1½ tablespoons of cold unsalted butter, 1½ tablespoons of light brown sugar, a pinch of salt, and ¼ teaspoon of ground cinnamon. Mix until resembling coarse crumbs, then fold in 1½ tablespoons of diced apples and refrigerate.

Preheat your oven to 425°F (220°C) and line a muffin pan with 4 liners.

In a large mixing bowl, whisk together 1½ tablespoons of sour cream, 5 tablespoons of pumpkin, 1 tablespoon of apple juice, 2 teaspoons of granulated sugar, 1½ tablespoons of light brown sugar, 1 large egg yolk, and ½ teaspoon of vanilla extract until smooth. Fold in ½ cup of diced apples.

In another bowl, whisk together ½ cup plus 1 tablespoon of flour, ¼ teaspoon of baking soda, ⅛ teaspoon of salt, and ¾ teaspoon of pumpkin pie spice. Gradually add this to the wet mixture, folding gently.

Distribute the batter into the muffin liners, filling each two-thirds full. Sprinkle the chilled streusel on top and bake at 425°F for 5 minutes, then lower to 350°F (175°C) and bake for another 11-13 minutes.

Let cool in the pan for 10 minutes before transferring muffins to a wire rack.