Add the condensed milk, the butter, and the chocolate powder to a medium sauce pan and stir.
Cook over medium heat, for approximately 10 mins, stirring repeatedly, scraping the sides and the bottom of the pan with a spatula to avoid burning.
The brigadeiro is ready when you scrape the bottom of the pan, and the brigadeiro takes 2-3 seconds to come back to its place, or when the mixture reaches 205F-208F - You can use a candy thermometer, or just a regular food thermometer to check.
Pour the hot brigadeiro into a a dish, or plate, and let it cool - about 2 hours.
Meanwhile, pour sprinkles in a deep plate or bowl.
When the brigadeiro is cooled, butter your hands, and scoop 1/2 Tbsp to Tbsp portions and roll little balls.
Roll the little balls in the sprinkles.
Keep them in a cool place or in the refrigerator until serving time.