To prepare the ice cream:

1. Line a 9×13” or jelly roll pan with a large sheet of aluminum foil. Be sure the foil extends just beyond the sides of the pan for easy removal. Set aside.
2. In a large bowl or the bowl of a stand mixer, whip the cream and clear vanilla extract on medium speed until it thickens to fluffy, stiff peaks. Fold in the sweetened condensed milk, being careful to not overwork, followed by the sprinkles. Spread it into the prepared pan. Freeze until solid, at least 6 hours but preferably overnight.

To make the cookies:

1. Preheat the oven to 350 degrees. Prepare sheet pans by lining them with silicone baking mats or parchment paper.
2. In a large mixing bowl or the bowl of a stand mixer, cream the butter, sugar, and brown sugar on medium speed until light and fluffy, about 2 minutes. Scrape the sides of the bowl and add the vanilla and egg, beating on low until incorporated. Add the flour, baking soda, salt, and cream of tartar, and beat on low speed just until the dry ingredients are combined. Scrape the sides of the bowl and add the sprinkles. Beat just until combined.
3. Chill the dough in the fridge until it has thickened to a Play-Doh consistency- usually about 30 minutes in the fridge for me. Once chilled, scoop out 1-1/2 tablespoon sized scoops (I use a medium cookie scoop) and roll each dough ball briefly in your hands to smooth out the rough edges of dough. Place on the prepared baking sheets 2 inches apart. Bake in the preheated oven for about 11-12 minutes, or until the tops of the cookies have just begun to crack and the edges are set. They will look slightly underbaked- this will help to keep them soft even when frozen. Allow to cool on the sheet pans for about 5 minutes before removing to a cooling rack to complete cooling.

To assemble the sandwiches:

1. Use a large round cookie cutter or the lip of a wide-mouth mason jar to cut out rounds of ice cream. Place in between two cookies and refreeze the sandwiches quickly. You can save the leftover edges of the ice cream in a sealable container or freezer-safe bowl. Keep the sandwiches covered while in the freezer to protect their taste.