Preheat oven to 375°F (190°C). Line baking sheets with parchment paper.
In a medium bowl, whisk together flour, baking soda, baking powder, and salt.
In a large bowl, cream butter and sugar until light and fluffy.
Beat in the egg, vanilla extract, and almond extract (if using).
Add sour cream and mix until smooth.
Gradually add dry ingredients and mix until just combined.
Scoop dough onto baking sheets, spacing 2 inches apart.
Bake 8–10 minutes, until edges are lightly golden but centers remain soft.
Cool on the baking sheet for 5 minutes, then transfer to a wire rack.
For the icing, whisk powdered sugar, milk, and vanilla until smooth.
Adjust consistency with more milk or powdered sugar as needed.
Divide icing, add gel coloring, and decorate cooled cookies. Add sprinkles if desired.