Boil the water, sugar, and condensed milk in a pot for 1 minute, then remove from heat.
Bloom the gelatin sheets in 8 cups (2 liters) of cold water for 5 minutes, then wring the gelatin sheets of excess water and mix into the sugar mixture.
Pour the liquid over the chocolate, letting it sit for 2-3 minutes to allow the chocolate to soften.
Using an immersion blender, carefully blend the chocolate and the liquid, making sure that you are not blending in air bubbles by lifting up the blender too high. It’s okay to go slow, just make sure it’s all blended with as little bubbles as possible, which will show up in the final product.
Sieve the mix into a large jug or vertical container to remove any excess bubbles. If there are still bubbles, continue to sieve back and forth. A trick to remove air bubbles from the surface is to manually pop them with a toothpick or to press cling film into the surface and remove the bubbles.
Separate the glaze into different containers and color them to your desire.
We used red and white for this cake. Blend the coloring with the glaze until the color is distributed evenly, then cover each container with the cling film, pressing the film into the glaze to ensure that there is no skin when you are ready to use the glaze.
When you are ready to use the glaze, make sure each one is around 90-96°F, then pour the colored glazes back into one container. Swirl them if you’d like, then glaze your cake!