In a large mixing bowl, beat the softened butter and 150 grams powdered sugar until smooth, pale, and fluffy, about 2 to 3 minutes.
Mix in the vanilla extract, almond extract, and whole milk until fully combined. The mixture may look slightly soft, which is normal.
In a separate bowl, whisk together the all-purpose flour, cornstarch, and fine salt so the dry ingredients are evenly distributed.
Add the dry ingredients to the butter mixture and mix on low speed just until a soft dough forms with no dry pockets. Do not overmix.
Divide the dough in half and shape each half into a log about 4 centimeters thick. Wrap each log tightly and chill for 60 minutes, or until firm enough to slice cleanly.
Preheat the oven to 175°C and line two baking sheets with parchment paper.
Unwrap the chilled dough and slice into rounds about 1 centimeter thick. Arrange the cookies on the prepared baking sheets, leaving a little space between each one.
Bake one sheet at a time for 10 to 12 minutes, until the bottoms and edges are just beginning to turn light golden while the tops remain pale.
Let the cookies cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely.
Once fully cooled, dust the tops with the remaining 30 grams powdered sugar before serving or packaging.