E.L. Fudge-Style Chocolate and Vanilla Sandwich Cookies Recipe

Name: E.L. Fudge-Style Chocolate and Vanilla Sandwich Cookies Recipe
Total time: 75 min
Yield: 24
Ingredients: For the Cookies:; 3 1/2 ounces sugar (about 1/2 cup; 100g); 1/4 teaspoon (1g) Diamond Crystal kosher salt; for table salt, use about half as much by volume or use the same weight; 1/2 teaspoon baking powder; 4 ounces unsalted butter (about 8 tablespoons; 115g), pliable but cool; 1 ounce milk (about 2 tablespoons; 30g), any percentage will do; 1/2 ounce vanilla extract (1 tablespoon; 15g); 7 3/4 ounces all-purpose flour (about 1 3/4 cups, spooned; 220g), plus more for dusting; For the Filling:; 4 ounces powdered sugar (about 1 cup, spooned; 110g); 1 ounce Dutch-process cocoa powder (about 1/4 cup, spooned; 30g), such as Cacao Barry Extra Brute; 3 ounces unsalted butter (about 6 tablespoons; 85g), brought to about 72°F (22°C); 1/4 teaspoon vanilla extract; 1/8 teaspoon (1/2g) Diamond Crystal kosher salt; for table salt, use about half as much by volume or use the same weight