Preheat your oven to 350°F and spray your mini Bundt pan with non-stick spray.
In a large mixing bowl, add the two eggs and whisk until frothy, for roughly 60-90 seconds. Add in 2/3 cup sugar and whisk until fully combined.
Add 1 cup of milk and 1/2 cup of pumpkin puree and whisk until combined.
Add 1/2 cup of melted butter, 3/4 teaspoon baking powder, 1/4 teaspoon baking soda, 2 teaspoons pumpkin spice mix, 1 teaspoon vanilla extract, and 1/4 teaspoon salt. Whisk until combined.
Add the flour in next. Start with a 1/2 cup at a time until you get to the full amount of 2 cups.
Fill each Bundt pan cup about 2/3 to 3/4 full. Bake for 30 minutes or until a toothpick inserted in the thickest part comes out mostly clean.
Let the cakes rest for 10 minutes before removing them from the pan to cool completely on a wire rack. Be sure the cakes are fully cooled before adding any toppings.
You can use any decorating tip you like to pipe the frosting onto the Bundts. I like using the star tip. Pipe roughly 2 tablespoons of frosting onto each Bundt, or to your taste.