Creating these incredible muffins is straightforward. Follow these simple steps for the best results:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or grease it lightly.
2. Mix Dry Ingredients: In a large bowl, combine 2 cups of flour, granulated sugar, baking powder, 1 teaspoon of cinnamon, and salt. Whisk together until well blended.
3. Combine Wet Ingredients: In another bowl, whisk together the melted butter, egg, vanilla extract, and milk until fully combined.
4. Mix Together: Pour the wet ingredients into the dry ingredients. Stir gently until just combined, being careful not to overmix.
5. Add Apples: Fold in the diced apples until evenly distributed throughout the batter.
6. Prepare Crumb Topping: In a separate bowl, mix together the brown sugar, oats, ½ cup flour, 1 teaspoon cinnamon, and softened butter. Use your fingers or a fork to create a crumbly texture.
7. Fill Muffin Tin: Divide the muffin batter evenly among the prepared muffin cups, filling each about 2/3 full.
8. Add Topping: Generously sprinkle the crumb topping over each muffin.
9. Bake: Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
10. Cool: Once baked, remove the muffins from the oven and allow them to cool in the tin for about 10 minutes before transferring them to a wire rack to cool completely.

These steps will help you create the most delicious Apple Cinnamon Crumb Muffins with ease!