Whisk together flour, baking powder, and salt in a medium bowl.
In a separate large bowl, cream butter and sugar with an electric mixer until light and fluffy, about 3 minutes.
Add egg, vanilla, and almond extract, beating until fully incorporated.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Don't overmix once the flour is added.
Divide the dough in half. On a lightly floured surface, roll each portion to ¼-inch thickness.
Use a sweater-shaped cookie cutter to cut out shapes. If you don't have a specialized cutter, use a template made from cardboard and cut around it with a knife.
Transfer cookies to parchment-lined baking sheets, leaving 1 inch between each cookie.
Bake at 350°F for 10-12 minutes, or until edges are just barely golden. The centers should remain soft and pale.
Allow cookies to cool completely on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely.
In a stand mixer fitted with the paddle attachment, combine powdered sugar and meringue powder.
Add water and vanilla, starting with 6 tablespoons of water. Mix on low speed until combined, then increase to medium-high and beat for 5-7 minutes until stiff peaks form.
Divide icing into small bowls and color with gel food coloring. Transfer to piping bags fitted with small round tips or use squeeze bottles.
First, outline each cooled cookie, then flood with icing. Add designs like zigzags, stripes, dots, or Nordic patterns before the base dries.
Add sprinkles, sanding sugar, or candy pearls while the icing is still wet.
For a "sweater texture," gently tap the wet icing with a clean, dry brush to create tiny peaks across the surface.
Allow cookies to dry completely for several hours or overnight before stacking or packaging.