With an electric beater or stand mixer beat the butter until it is light and fluffy ( usually looks whiter in color)
Sieve powdered sugar into a bowl and add to the butter a few tablespoons at a time until fully combined.
Add cream, cinnamon, and vanilla to the buttercream and beat well until it is smooth and shiny.
Place in a piping bag with your preferred piping tip and pipe onto the top of the cooled cupcakes.
Decorate as desired ( I topped with mini gingerbread cookies to decorate)