In a large mixing bowl, combine butter, sugar and egg. Beat with an electric mixer until light and fluffy.
Add vanilla extract and beat until combined.
In a separate bowl, sift flour, baking soda, cream of tartar and salt.
Add flour mix to wet ingredients. Beat until just combined. Stir in sprinkles.
Cover and chill in refrigerator for 1 hour.
Preheat oven to 350°F. Line a baking sheet with parchment paper. Scoop batter with 2 tablespoon scoop onto prepare baking sheet, placing them 2" apart. Bake for 10-11 minutes (they will look underdone - this is normal). Allow to cool completely.
Scoop approx ½ cup of ice cream onto the flat side of 6 of the 12 cookies. Top with flat side of left over cookies to make a sandwich.