Place 4 oval tubes measuring 5cm/2in wide by 25cm/10in long in a standing position over a flat sheet pan lined with a 3-mm/.12-in thick sheet of rolling fondant. The dimensions should be a square that measures 15cm/6in on each side; roll it out by hand or using a sheeter. Push the molds gently into the fondant and then tape the molds together so that they don’t tilt or fall over. This will ensure that the liquid does not seep through the tubes. It also helps to keep the tubes in place. The tubes do not need to be lined because once the cream sets, it can be gently pushed out without it sticking to the tube.
Combine the heavy cream and the vanilla paste in a small sauce pot. Combine the sugar, agar-agar, and locust bean gum in a small bowl using a whisk. Shear this mixture into the cream using a handheld immersion blender. Since it is cream, it needs to be tempered; otherwise when you shear the agar and locust bean gum in, it will whip. Tempered cream does not whip.
Bring the liquid to a boil while shearing. Let it boil for 5 seconds, then turn off the heat.
Pour the cream into the prepared tubes and refrigerate.
Once the cream has set, it can gently be pushed out of the tubes or reserved in the refrigerator for up to 3 days.