Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper for easy cleanup.
In a large mixing bowl, beat the softened butter until light and fluffy—about 2 minutes.
Pour in the sweetened condensed milk and mix until the two are fully combined. This mixture should look creamy and smooth.
Sift in the all-purpose flour and baking powder. Stir gently with a spatula or slow electric mixer until a soft dough forms. Be careful not to overmix; you want the cookies to stay tender.
Using your hands or a small cookie scoop, roll the dough into 1-inch balls and place them about 2 inches apart on the prepared baking sheet.
Bake for 12-15 minutes, or until the bottoms are just turning golden but the tops remain pale—do not overbake!
Let the cookies cool for a few minutes on the baking sheet, then roll each one in confectioner’s sugar while they’re still slightly warm to ensure the sugar sticks.
For a classic snowball effect, roll the cookies in sugar a second time once they have cooled completely.
Notes
Store cookies in an airtight container at room temperature for up to 1 week. For longer storage, freeze for up to 3 months.