Make the crumb topping: Whisk together the flour, brown sugar, cinnamon, nutmeg, and salt in a medium bowl. Add the cubed butter, and mix with a pastry blender or a fork until the mixture forms crumbs, then set aside.
Preheat oven to 375°F. Line or grease muffin pan.
Make the muffins: Whisk together the flour, baking powder, and salt; then set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or using an electric hand mixer, beat the butter, brown sugar, and cookie butter on medium speed until thoroughly combined. Add the egg and vanilla, and mix until incorporated.
Reduce the mixer speed to low and alternate adding the dry ingredients and the milk in three portions (be sure to start and end with adding the dry ingredients). Mix until just combined.
Divide the batter amongst the muffin cups, using about 4-5 tablespoons of batter in each cup. Sprinkle the desired amount of crumb topping over the muffin batter.
Bake 20 – 25 minutes, or until the muffins are lightly browned and a toothpick inserted into the center comes out clean. Cool the muffins in the pan for 10 minutes. Then transfer them to a wire rack to cool completely.