First, mix together the egg, both sugars, butter, milk, and vanilla until all ingredients are incorporated together.
In a separate bowl, stir together the dry ingredients (flour, baking powder and soda, cinnamon, nutmeg, allspice, cardamom, and salt).
With the mixer still turning on low speed, slowly add the dry ingredients to the wet ingredients. This will come together quickly, so don't overmix.
Then, with the mixer still turning, slowly pour in the apple cider reduction.
Finally, mix in the shredded apple.
Grease your muffin pan with melted butter and fill each cup to about two-thirds full. Sprinkle cinnamon streusel on top of each one.
Bake at 350°F for 20 minutes or until a toothpick inserted in the center comes out clean.
Enjoy with a glass of apple cider or a steaming mug of hot tea.