Line a baking sheet with parchment paper and spray with cooking oil; set aside.
In a large bowl cream together the sugar with ½ cup shortening using an electric mixer. Add eggs and continue to mix until well combined.
Add flour, baking soda, salt, buttermilk, vanilla and cardamon and blend on low speed for one minute. Increase speed to medium and continue to mix for an additional two minutes ensuring to scrape down the sides.
Scoop one tablespoon of batter onto the prepared pan about an inch apart. Bake in the oven for 8-10 minutes until no indentation appears when the top is lightly touched.
Let cool on cookie sheet for two minutes and then transfer to a cooling rack until cooled.
While cookies are cooling prepare the filling. Combine all ingredients in a medium bowl. Using an electric mixer beat on low for one minute.
Add desired amount of food colouring, increase speed to high and continue to beat for an additional two minutes. Refrigerate until ready to use.
To assemble cookies place a dollop of icing on the centre of the flat side of one cookie. Top with another cookie and press gently together to evenly spread the icing. Repeat for all cookies.