In a medium saucepan over medium-high heat, add one tablespoon of butter, sweetened condensed milk, and Nestle Quik. Using a silicone spatula stir the mixture until well blended and smooth.
Continuously stir the mixture for about 10 minutes until it starts to thicken and begins to bubble around the edges. Reduce the heat to a slow simmer to keep the mixture from burning.
As the mixture continues to thicken, you'll notice that when you scrape the batter with the spatula, it will start to pull away from the sides and bottom of the pan, staying together without spreading, this means that the mixture is ready. Or when it reaches 205-208 degrees on a candy thermometer.
Transfer the brigadeiro mixture to a medium bowl and chill in the refrigerator until set, about 30 minutes. Or, leave on the countertop for about 2 hours.
When the brigadeiro mixture is cooled, use the remaining butter to butter your hands and then scoop tablespoon portions. Roll the pieces into small balls and coat them in chocolate or rainbow sprinkles. Place each brigadeiro into a paper cup if you choose.
Store the brigadeiro in the refrigerator or cool place until ready to serve. Brigadeiro will keep for about 3 days.