Preheat oven to 400°F (200°C). Line baking sheets with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, beat 1 cup (227 grams) butter and ½ cup (60 grams) confectioners’ sugar at low speed; slowly increase mixer speed to medium, beating until light and creamy, 3 to 4 minutes, stopping to scrape sides of bowl. Beat in 1 teaspoon (6 grams) vanilla bean paste.
In a medium bowl, whisk together flour and ½ teaspoon (1.5 grams) salt. With mixer on low speed, gradually add flour mixture to butter mixture, beating until a dough forms. Using a 1½-tablespoon spring-loaded scoop, scoop dough (about 24 grams), and roll into balls.
In a small bowl, stir together white sparking sugar and 1 tablespoon (12 grams) vanilla sugar. In another small bowl, stir together blue sparkling sugar and remaining 1 tablespoon (12 grams) vanilla sugar. Roll half of dough balls in each sugar mixture, and place 3 inches apart on prepared pans; leave rounded, or gently press into 2-inch disks for a flatter sandwich cookie.
Bake, one batch at a time, until edges are lightly golden, 8 to 10 minutes, rotating pan halfway through baking. Let cool on pan for 3 minutes. Remove from pan, and let cool completely on wire racks.
Clean bowl of stand mixer and paddle attachment. Using the paddle attachment, beat remaining ¾ cup (170 grams) butter and remaining ¼ teaspoon salt at medium speed until smooth, 2 to 3 minutes. Beat in honey and remaining 1 teaspoon (6 grams) vanilla bean paste. With mixer on low speed, gradually add remaining 2 cups (240 grams) confectioners’ sugar, beating until combined. Add cold cream; increase mixer speed to medium-high, and beat until light and fluffy, 1 to 2 minutes.
Spoon buttercream into a pastry bag fitted with a large round piping tip (Wilton 1A). Pipe buttercream onto flat side of half of cookies. Place remaining cookies, flat side down, on top of buttercream. Serve immediately.
Recipe by Bake from Scratch at https://staging.bakefromscratch.com/holiday-glitter-sandwich-cookies/