Preheat the oven to 425 degrees. Line a muffin pan with liners and spray lightly with nonstick cooking spray.

To make the muffins:

In the bowl of a stand mixer, cream the butter and sugar at medium speed until light and fluffy.

Add the eggs, one at a time, scraping down the bowl after each addition.

Add the baking powder, nutmeg, salt, and vanilla extract to the bowl and mix until just combined.

Beginning and ending with the flour, alternate adding the flour and eggnog to the bowl, mixing at low speed, just until each ingredient is incorporated.

Scoop the batter evenly into the prepared muffin cups.

To make the topping:

Use a fork to combine all of the ingredients just until the mixture is crumbly.

If you mix too much, it will form into a cohesive ball, not a crumbly topping.

Sprinkle the topping evenly over the batter.

Allow to cool for a few minutes in the pan, then transfer the muffins to a wire rack to cool before serving.