Preheat your oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or grease thoroughly with butter or cooking spray.
In a medium bowl, combine the flour, brown sugar, and all spices for the streusel. Whisk them together to ensure even distribution of the aromatic chai spices.
Add the cold butter cubes to the streusel mixture and use your fingertips or a pastry cutter to work the mixture until it resembles coarse crumbs.
In a large bowl, whisk together the flour, baking powder, salt, cinnamon, cardamom, ginger, cloves, and black pepper for the muffin batter.
In a separate bowl, whisk together the sugar and melted butter until combined. Add the eggs one at a time, whisking well after each addition. Stir in the milk and vanilla extract until the mixture is smooth and well incorporated.
Pour the wet ingredients into the dry ingredients and stir gently with a spatula just until combined. Be careful not to overmix.
Gently fold in the diced apples until evenly distributed throughout the batter.
Divide the batter evenly among the prepared muffin cups, filling each about ¾ full. Use an ice cream scoop for consistent portioning if available.
Sprinkle the chai streusel topping generously over each muffin, gently pressing it into the batter slightly to ensure it adheres during baking.
Bake for 22-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean or with just a few moist crumbs. The tops should be golden brown and slightly firm to the touch.
Allow the muffins to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.