Better Than Store-Bought Cookies - Cook with Carla

Ingredients

• Softened unsalted butter, 1 cup (used for cookies).
• Sugar, granulated, 3/4 cup.
• Dark brown sugar, 3/4 cup.
• 1 large egg.
• All-purpose flour, 1 2/3 cups.
• Unsweetened cocoa, 2/3 cup.
• Salt, 1 teaspoon.
• Baking soda, 1/2 teaspoon.
• More softened butter (3/4 cup) for the filling.
• Powdered sugar (confectioners'), 2 cups.
• Milk, 1 tablespoon.
• Vanilla extract, 1/2 teaspoon.
• Kosher salt, 1/2 teaspoon (used in filling).