Preheat Oven & Prepare Pan: Preheat oven to 375°F (190°C) and grease a 12x17-inch baking sheet.
Mix the Dough: Cream together butter and sugar until light and fluffy. Beat in eggs and vanilla extract. In a separate bowl, whisk together flour, salt, and baking soda, then mix into wet ingredients until combined.
Bake the Cookie Base: Spread dough evenly in the prepared baking sheet. Bake for 15 minutes or until edges are lightly golden. Let cool completely.
Make the Frosting: Beat butter until smooth, then add powdered sugar, milk, almond extract, and green food coloring. Mix until creamy.
Frost & Decorate: Spread frosting evenly over the cooled cookie base. Sprinkle with St. Patrick’s Day-themed sprinkles.
Slice & Serve: Cut into bars and enjoy!