Heat 3 inches of oil in a heavy bottomed pot to 375 degrees. I keep a candy thermometer in the oil so that I can watch the temp and adjust accordingly. See recipe notes below or in post for tips on frying.
In a small bowl, combine the flour, baking soda, salt and nutmeg. Set aside.
In a large bowl, combine the softened butter with sugar using a hand mixer. Next add egg and mix until combined. Then add the egg nog, bourbon and vinegar.
Gradually add the flour mixture until combined.
Once the oil has reached 375 degrees, carefully place one mound of batter into the hot oil using a small cookie scoop or a 1 tablespoon measuring spoon. Check the timing and level of doneness for this first donut and adjust the heat and timing if needed.
Continue frying the donuts in batches. Don’t crowd the pan and monitor the oil temp, adjusting as needed. The temp will fall quickly once you add the batter. You need to keep it between 360-380 degrees to fry properly. Using a long handled spoon, turn the donuts several times while cooking for 4-5 minutes.
They will be well browned when done, but not burnt. Remove from hot oil and rest for a moment on paper towels. Roll the donuts in granulated sugar while warm.