Once melted, add the condensed milk, dulce de leche and cinnamon, mix until you get a homogeneous mixture and all the ingredients have incorporated together.
Continue mixing non-stop until you can see the bottom for 3-5 seconds when you run a spoon across the diameter of the pan. The mixture should be much thicker now. This process will take about 15 minutes.
Place the brigadeiro fudge on a greased plate or bowl and let it cool for about 30 minutes to 1 hour in the refrigerator.
To roll the brigadeiros:
In a small bowl, combine the sugar with the cinnamon.
With buttered hands and with the help of a spoon or a small cookie scoop, scoop some of the brigadeiro fudge and roll between your palms to form a smooth ball.
Roll each ball over the cinnamon sugar and place in a serving plate or small baking cups. Do this process until you are done with the mix. You should have 18-20 brigadeiros depending on the size.
Optional: In a small microwave safe bowl, carefully melt the chocolate in 30 second intervals or with the ‘melt chocolate’ setting of your microwave if available. Be careful not to burn it or it will seize. Transfer to a small piping bag and trim the tip just a tiny bit. Drizzle the brigadeiros in zig-zag motion with chocolate.
Store the brigadeiros in the refrigerator and serve cold.