1. Preheat your oven to 375°F. Line a muffin tin with 12 paper liners and set aside.

2. In a medium bowl, mix together all the ingredients for the streusel until combined and you’re left with a crumbly mixture. Set the streusel aside in the fridge while you prep the other parts.

3. In a large bowl, combine flour, both sugars, baking powder, cinnamon, salt, and butter.

4. Use a fork, your fingers, or an electric mixer fitted with the paddle attachment to cut the butter into the dry ingredients until the mixture resembles moist sand.

5. Push the dry ingredients off to the sides of the bowl to create a well in the center. Add in the eggs, milk, oil, and vanilla.

6. Whisk the wet ingredients in the center to break them up and then incorporate the dry ingredients until you have a streak-free batter. A few small clumps are fine.

7. Divide the muffin batter into the prepared muffin cups, filling each one just a little below full. Set aside.

8. In a medium bowl, toss together apples, sugar, and cinnamon to combine.

9. Evenly spoon about 1 tablespoon of the apple mixture on top of the batter in each muffin cup.

10. Take the streusel out of the fridge and use a fork to break it up into smaller pieces. Sprinkle it evenly on top of each muffin.

11. Bake in the center of your preheated oven for 20–25 minutes or until a skewer inserted into the center comes out clean with a few moist crumbs.

12. Cool the muffins for 5–10 minutes in the pan, then move them onto a wire rack to finish cooling to slightly warm or room temperature.

13. (Optional) In a medium bowl or cup, whisk together powdered sugar and 1 tablespoon of water or milk until smooth and pourable. Adjust consistency as needed and drizzle over muffins.