- 1 1/2 cups unsalted butter, room temperature
- 1 3/4 cups sugar
- 2 large eggs
- 1 teaspoon salt
- 2/3 cup evaporated milk
- 1 tablespoon pure vanilla extract
- 1 vanilla bean, split and scraped (optional)
- 5 cups all-purpose flour, plus more for pressing cookies
- Coarse sanding sugar, for rolling
- Chocolate Fudge Filling (http://www.marthastewart.com/256430/chocolate-fudge-filling)
- In the bowl of an electric mixer fitted with the paddle attachment, mix together butter and sugar on medium speed until light and fluffy, about 3 minutes. Add eggs and salt; mix to combine. Add evaporated milk, vanilla extract, and vanilla bean seeds, if using; mix to combine.
- Reduce speed to low; slowly add flour. Mix until just combined; do not overmix. Divide dough into 4 equal pieces and shape each piece into a disk. Cover tightly with plastic wrap. Transfer to refrigerator and chill until firm, at least 1 hour.
- Preheat oven to 350 degrees. Line two baking sheets with nonstick baking mats or parchment paper.
- Working with one disk at a time, form dough into 1-teaspoon-sized balls. Roll each ball in sanding sugar and place on prepared baking sheet, about 2 inches apart. Lightly dip the bottom of a drinking glass in flour and gently press down on ball to flatten slightly. Transfer baking sheets to oven and bake until puffy, but still soft, 8 to 10 minutes. Let cool slightly on baking sheets before transferring to a wire rack to cool completely.
- Using a small offset spatula, carefully spread about 1 teaspoon filling on the flat side of one cookie; top with another cookie to make a sandwich. Repeat process with remaining filling and cookies.
Cookies can be kept in an airtight container at room temperature for 2 to 3 days.