For the Cookies:

Cup of Yum
1. To the bowl of a stand mixer fitted with the paddle attachment (or mixing bowl and hand mixer), add the butter and beat to soften and fluff it, about 1 minute.
2. Add 1/4 cup granulated sugar, vanilla, and beat to cream ingredients until fluffy, about 3 to 4 minutes, stopping to scrape down the sides of the bowl as necessary.
3. Add the flour and mix to incorporate it. The dough will be very sandy, pebbly, and dry. Add two tablespoons of half-and-half or cream and mix. The dough will come together and it will be on the soft and sticky side. If your dough is sandy and dry and hasn’t come together, add 1 additional tablespoon of cream, or as needed, so it combines. I used 2 tablespoons and cannot foresee needing more than 3 tablespoons of cream, but add cream very, very slowly until it combines.
4. Wrap dough in plastic wrap and transfer it to an airtight container and refrigerate it for at least two hours, or up to five days, before rolling it out.
5. Turn the dough out onto a floured Silpat Non-Stick Baking Mat or floured countertop and cover it with a piece of plasticwrap to prevent it from sticking to the rolling pin. Roll dough out to about one-eighth inch thick.
6. Using a 2-inch cookie cutter or biscuit cutter, cut out the dough into rounds (or if desired, cut them smaller in the one-inch range. Use a shotglass if you don't have a one-inch cutter). Re-roll your scraps and use every last bit of dough until it’s gone. I made 26 rounds to yield 13 sandwiches.
7. Place rounds on a Silpat-lined, parchment-lined, or cooking sprayed baking sheet. I fit them all on one sheet. If dough has gotten soft while rolling and cutting it out, cover and refrigerate the tray for about an hour, which will help prevent spreading.
8. Preheat oven to 350F. Before baking, place about 1/2 cup granulated sugar in a shallow bowl and dredge each dough round through the sugar and return sugared rounds to baking sheet. Piece each round three or four times with the tines of a fork to give steam a place to escape so the cookies bake flat and don’t puff up while baking.
9. Bake for 7 to 9 minutes or just until they've set, rotating trays halfway through baking. I baked for 8 minutes. They’ll look glossy and shiny even when they’re done. Don’t let them turn brown in the least, and pull them even if they look underdone because they firm up as they cool. Don’t leave the kitchen and watch them like a hawk because they're small, full of butter, white flour, sugar, and are highly prone to burning.
10. Allow cookies to cool for about 5 minutes on baking trays before transferring to a wire rack to finish cooling.

For the Buttercream:

1. While the cookies cool, make the buttercream. Beat one stick of butter to soften and fluff it, about 1 minute.
2. Add 1 1/2 cups confectioners’ sugar (I don't bother sifting), vanilla, and beat until soft and fluffy, about 5 minutes. Play with the sugar ratio depending on how thick you like your buttercream. I find 2 cups sugar gives me a frosting that’s just right for a job like this when I want a firmer frosting, but if you like looser frosting, 1 1/2 cups will probably do the trick.
3. Add food coloring very slowly, in the color of your choice, and mix to incorporate.
4. Frost one cookie generously with 1 to 2 tablespoons frosting, top with another cookie, sandwich them together, and lightly squeeze. Repeat until all cookies have been sandwiched. I don't bother with a pastry bag and use a knife and spoon.