Preheat oven to 350 degrees. Line 2 baking sheets with parchment paper.
In a the bowl of your mixer, beat butter and sugar until light and fluffy.
Add eggs, one at a time, and vanilla extract; beat until well mixed.
Add flour, baking soda, cinnamon and salt; beat at low speed, scraping bowl often, until well mixed.
Stir in carrots, rasins, and oats.
Drop rounded tablespoonfuls of dough onto greased cookie sheets.
Bake 11-13 minutes or until lightly browned around edges. Cool completely.
To make the frosting, beat butter, cream cheese, vanilla, and powdered sugar until smooth.
Once cookies are completely cooled, spread about 1 tablespoon icing on flat side of 1 cookie; top with another cookie, flat side down.
Repeat with remaining cookies and filling. Makes approximately 1 dozen cookie sandwiches.