Squeeze out the juice. Pour the remaining water over the carrots and cook for 15 minutes. strain the broth.
Mix the prepared broth with the squeezed juice and sugar, bring to a boil, add the dissolved gelatin and bring to a boil again. Cool the cooked mass before gelling and whisk until a persistent foam forms. Pour into molds and cool until thickened.
Before serving, dip the molds in hot water for a few seconds and put the mousse on a dish.