In a large mixing bowl, add sugar, melted butter, eggs, vanilla, pumpkin, cinnamon, ginger, nutmeg, cardamom, flour, salt, baking powder and milk then mix well.
Add all streusel topping ingredients together in a separate bowl until a crumble forms.
Spoon batter into a lined or greased muffin tin so it is roughly 2/3 of the way full then sprinkle the tops of muffin batter with the streusel topping.
Bake muffins for about 18-20 minutes or until the tops of muffins spring gently back when pressed on with your finger or a toothpick can be inserted and come out clean.