In a large mixing bowl, add the flour, sugar, baking powder, salt, and cinnamon. Add these together and stir them until they are well combined, then make a well in the center.
In a medium bowl or a large measuring cup, whisk together the eggs and eggnog, then add the oil and bourbon. Mix thoroughly, then pour the wet ingredients into the well in the center of the dry ingredients. Use a large spoon to stir, making sure all of the flour gets incorporated, but being careful not to overmix.
Use a tablespoon to pour the batter evenly into the muffin cups. Top the batter with the streusel, pressing it slightly into the batter. Bake at 400° F (200° C) for about 15-18 minutes, or until the tops bounce back when touched. Let them cool for about 30 minutes before glazing.