To Make the Whoopie Pies:

1. Preheat oven to 400°F. Line a baking sheet with parchment paper and set aside.
2. In a large bowl, beat cake mix, eggs, and water on medium speed until fully combined.
3. Drop batter using a small cookie scoop on prepared baking sheet and bake for about 6-8 minutes or until tops spring back when lightly touched.
4. Remove to a wire baking sheet to cool.

To Make the Frosting:

1. In the bowl of your mixer, beat butter, cream cheese, and vanilla on medium speed until smooth.
2. With the mixer on low, slowly add powdered sugar and cinnamon. Beat until smooth.
3. Add heavy cream and increase speed to medium high. Beat until light and fluffy, about a minute.
4. Frost the flat side of half of the cookies, then top with another cookie.