In the bowl of a stand mixer cream butter for 2 minutes.
Add condensed milk and beat until soft and fluffy, scraping the sides of the bowl to make sure everything is evenly distributed.
Add flour (self rising or regular flour mixed with baking powder, 1 cup of flour + 1.5 tsp baking powder + 0.5 tsp of salt) and mix until incorporated, but do not over mix the dough.
Roll dough into balls of your preferred size.
Line cookie sheets with parchment paper and place cookie balls, leaving at least 1.5 inches between each cookie.
Chill cookies for 2 hours before baking.(Optional, but I recommend it if you don't want your cookies to spread).
When ready to bake, preheat oven to 325 F (160 C).
Bake for 10 - 12 minutes, until edges turn golden. Make sure you keep an eye on cookies, while baking, because they can easily burn.