Vanilla Whoopie Pies with Sprinkles

Ingredients

• 2 1/2 cups all-purpose flour
• 1 1/4 teaspoons baking soda
• 1/4 teaspoon salt
• 1 cup granulated sugar
• 1/2 cup (1 stick) Nellie's Free Range Unsalted Butter, softened
• 1 large Nellie's Free Range Egg
• 2 teaspoons vanilla extract
• 3/4 cup whole milk
• Sprinkles for decorating
• 1 cup (2 sticks) Nellie's Free Range Unsalted Butter, softened
• 4 cups powdered sugar, sifted
• 1/2 teaspoon salt
• 2 to 4 tablespoons milk
• Food coloring
• Piping bag with round tip (or a zip-top bag)