Spritz liners lightly with your favorite cooking oil spray [for easy liner removal]
Give your oats a quick whirl in a food processor to grind into a powder. It will be coarser than the flour but blend more beautifully into the muffins this way.
Combine freshly ground oats with eggnog and sit aside.
Next combine flour, salt, cinnamon, nutmeg, allspice and baking powder in a bowl and set aside.
Prepare your streusel crumb topping by combining all topping ingredients and stirring with a fork until crumbly.
In a medium bowl, use a stand or hand mixer to cream together softened butter and sugar until smooth.
Next mix in the egg on low speed for approx 2-3 minutes until your batter lightens in color.
Add vanilla and mix until incorporated.
Sift about 1/3 the flour mixture into the bowl and stir with a fork, then add 1/2 the eggnog/oat mixture, followed by another 1/3 of the flour mixture, the rest of the eggnog mixture, and finally the last of the flour.
Pour evenly into your lined muffin cups and top with a hearty crumble of streusel.
Bake approx 18 minutes [times vary a smidge from oven to oven] until golden brown.
Check to see if a toothpick comes out clean from the center and pop them out of the muffin tin to cool on a wire cooling rack.