In a medium bowl, add softened butter, brown sugar, nutmeg, and allspice. Using a hand mixer or stand mixer with fitted paddle attachment, beat until light and fluffy, about 4-5 minutes.
Gradually add in the eggnog, continuing to beat until incorporated. You should have a mixture that is soft, light and spreadable.
Open the can of biscuits and separate them. Use knife to gently score the middle of each biscuit lengthwise and then separate the biscuits in half to make a total of 16 circles.
Spread about 1 teaspoon of the butter eggnog mixture onto each circle. You should have a thin but visible layer on each biscuit half.
If you have extra filling, simply add it to any biscuit that looks like it has less than others. Make 4 lines of biscuits, stacking them on each other with the filling facing up.