1. Prepare the Crust:

1. Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
2. In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the egg and vanilla extract. In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until a soft dough forms.
3. On a floured surface, roll the dough to about 1/4-inch thickness. Use a sweater-shaped cookie cutter to cut out shapes. Place cookies 1 inch apart on the prepared baking sheets. Bake for 8-10 minutes, or until the edges are just lightly golden. Let cool completely on a wire rack.
4. For the icing, whisk together the powdered sugar, 3 tablespoons of milk, corn syrup, and vanilla extract until smooth. Add more milk, a teaspoon at a time, if needed to reach a pipeable consistency. Divide the icing into small bowls and tint with food coloring. Decorate the cooled cookies to resemble Christmas sweaters with patterns, stripes, and ‘woolly’ textures. Let the icing set completely before serving.