If using gelatin sheets, soak them in cold water for about 5-10 minutes until soft. If using powdered gelatin, sprinkle it over 60 grams of water and let it bloom for about 5-10 minutes.
Make the Sugar Syrup:
In a medium saucepan, combine 150 grams of water, granulated sugar, and sweetened condensed milk. Heat the mixture over medium heat, stirring occasionally until it just starts to boil.
Add Gelatin:
Remove the saucepan from heat and add the softened gelatin (squeeze out excess water if using sheets) or the bloomed powdered gelatin. Stir until the gelatin is completely dissolved.
Incorporate Chocolate and Cocoa:
Place the dark chocolate (chopped into small pieces if in a solid bar) and cocoa powder in a large bowl. Pour the hot mixture over the chocolate and cocoa. Let it sit for a minute to melt the chocolate.
Blend the Mixture:
Use an immersion blender to blend the mixture until smooth. Be careful to avoid incorporating air bubbles as they can affect the smoothness of the glaze.
Strain and Cool:
Strain the glaze through a fine-mesh sieve to remove any lumps or air bubbles. Allow the glaze to cool to about 30-32°C (86-90°F), which is the ideal pouring temperature.
Glaze the Cake:
Ensure your cake is completely smooth and chilled. Place the cake on a wire rack over a baking sheet to catch excess glaze. Pour the glaze over the center of the cake, allowing it to flow evenly over the sides. Use a spatula to gently help spread the glaze if necessary.