Add the sweetened condensed milk and sifted cocoa powder to a large, nonstick saucepan and mix until well combined and homogenous. 

Place the saucepan onto medium-low heat and add the butter, salt, and vanilla. Stir until the butter has melted and it begins to bubble and thicken.

Once you can pass your spatula through the batter without it running together for 1-2 seconds, remove the pan from the heat. Immediately scrape the fudge mixture onto a plate, then refrigerate for 1 hour to cool.

Once cooled, remove the brigadeiro from the fridge. Lightly grease your hands with cooking spray or oil, then use a cookie scoop or spoon to evenly portion out the mixture (around 1.5 tablespoons each). Roll the brigadeiro into balls, then toss them into chocolate sprinkles until fully coated.

Serve the brigadeiro immediately, or store them in an airtight container at room temperature for 2-3 days or in the fridge for a week.