Bloom the gelatin sheets in a large bowl of cold water for 10 to 15 minutes. If using powdered gelatin, bloom it with 60 g (2 oz) water, about six times its weight, then refrigerate for at least 20 minutes.
Place the glucose syrup, sugar, vanilla bean seeds, and water in a saucepan. Bring to a boil and cook until the temperature reaches 103 °C (217 °F). Stir occasionally without splashing the sides of the pan. If splashes occur, clean the sides with a damp pastry brush.
Pour the hot syrup through a fine mesh strainer over the sweetened condensed milk or the heavy cream, then add the bloomed gelatin, well squeezed if using sheets.
Gently mix with a spatula, then pour the mixture over the white chocolate and the food coloring into a tall, narrow container, such as a measuring jug or a container suitable for an immersion blender. Let it sit for one minute, then mix again with the spatula.
Using an immersion blender, mix carefully. This step should be done gently to avoid creating air bubbles.
Blend while holding the container slightly tilted and the blender at an angle, making sure the blade stays fully submerged at all times. Do not lift it out until the mixture is completely smooth.
Pour the glaze through a fine mesh strainer into an airtight container, then cover it directly on the surface with plastic wrap. Refrigerate.
The next day, gently reheat the glaze in a saucepan over a water bath or in the microwave until it reaches 38 to 40 °C (100 to 104 °F).
Remove the glaze from the water bath from time to time, stir, then return it to the water bath or the microwave. Repeat several times to avoid exceeding the desired temperature and to fully melt the glaze.
Pour the glaze into a tall, narrow container. Using an immersion blender, mix carefully for 3 to 4 minutes to eliminate all air bubbles.
Let the temperature drop to 33 to 34 °C (91 to 93 °F), depending on the desired fluidity, then glaze the frozen mousse cake straight from the freezer.