Preheat oven: Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper or a silicone mat.
Prepare the dough: In a medium bowl, whisk together flour, baking powder, baking soda, and salt. In a large bowl, beat the butter and sugar until light and fluffy, about 2-3 minutes. Beat in the sweetened condensed milk, eggs, and vanilla extract.
Gradually add dry ingredients: Gradually add the dry ingredients to the wet ingredients and mix until a dough forms.
Chill the dough: Chill the dough for at least 30 minutes or up to 2 hours.
Roll the dough: Roll the dough into balls, about 1 1/2 tablespoons each.
Roll in powdered sugar: Roll the balls in powdered sugar to coat.
Bake the cookies: Place the balls onto the prepared baking sheet, leaving about 2 inches of space between each cookie. Bake for 12-15 minutes or until the edges are lightly golden brown.
Optional: If using nuts, roll the balls in chopped nuts before baking.
Cool the cookies: Allow the cookies to cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely.