Soak the gelatine leaves in cold water according to the packet's instructions (I soak mine for 8-10 minutes).8 leaves gelatin Prepare strawberries: Clean the strawberries. Chop about ⅓ of the strawberries and set them aside. Keep about 2 or 3 for decorating purposes, if you wish. Puree the rest of the strawberries together with the sugar.1.7 lb strawberries + 4 tablespoons granulated sugar Dissolve gelatine: Squeeze the gelatin gently to remove excess water. Place the gelatin leaves in a saucepan and dissolve over very low heat. Do not overheat the gelatin, and do not let it start to boil. Dissolving the gelatin will take a very short time, not even a minute, so stay close and keep stirring.
Add strawberry puree: Take the saucepan off the heat and start mixing in the strawberry puree a very little at a time. Start by adding one tablespoon puree, incorporating it well, then add another tablespoon. After adding about ⅓ of the puree, you can start adding more than just one tablespoon at a time, but keep stirring well and continuously.
Refrigerate: Place in the fridge for about 30 minutes or until just starting to set (it might take less time than that, depending on your fridge, so start checking after 5-10 minutes already, the mixture should not set too much).
Whipped cream: Whip 1 ⅔ cup/ 375 ml of the heavy cream and vanilla sugar. Fill a little bit of it in a piping bag and pipe an edge on the bottom of the springform. Take the strawberry puree out of the fridge and fold in the chopped strawberries you set aside before and the whipped cream.1 ⅔ cup/ 375 ml from 2 cups heavy cream+ 2 tablespoons vanilla sugar Assemble: Place the ladyfingers with the sugared side on the outside inside the pan to form a tight ring around the springform base. Fill the mousse into the prepared form.5.5 oz ladyfingers Refrigerate for at least 4 hours or until the strawberry mousse is set.
Decorate: Whip the remaining heavy cream and decorate the cake. Slice the leftover strawberries and use them to decorate the charlotte as well.