Melt 4 tablespoons of butter and set aside to cool. If your eggs and eggnog are not at room temperature, place your eggs in a cup of warm water for 10 minutes and microwave your eggnog for 30 seconds.
Whisk the flour, sugar, baking powder, baking soda, nutmeg, and kosher salt together in a large bowl.
In a large measuring cup, whisk the eggnog, eggs, and vanilla and rum extracts.
Pour the wet ingredients into the flour mixture and fold together until mostly combined.
Finish mixing while drizzling in your melted and cooled butter. Set aside to rest for 15 minutes.
Heat a large nonstick skillet, or electric griddle, over medium-low heat. When warm, add a teaspoon or so of butter or oil if desired. Drop ¼ to ½ cup scoops of pancake batter into pan. It will spread out a bit. After 2-3 minutes, bubbles will start to form and pop on the surface of the pancake.
When the edges look dry and and the bubbles on top have popped, about 2 to 3 minutes, use a thin pancake spatula to gently lift one side and peek underneath.
If the pancake is golden brown, flip and cook on the other side for 1 to 2 minutes, or until the bottom of the pancake is golden.
Serve with butter and warm maple syrup or your favorite toppings.Makes 8 to 10 pancakes.