Strawberry Puree: Place the unsweetened frozen strawberries in a large bowl and thaw.  This may take a few hours.  Once thawed, put the  strawberries and their juice in the bowl of a food processor or blender and process the berries until they are pureed.  Pour the puree into a 2 cup (480 ml) measuring cup.  You should have about 1 1/4 cups of puree.  Add 1/4 cup (50 grams) of the sugar to start and stir until the sugar dissolves.  Taste and add more sugar if needed.  Can also add a little lemon juice to taste.

Store covered in the refrigerator for up to one week

Makes approximately 1 1/4 cups (300 ml).

Sponge Cake: Preheat oven to 350 degrees F (177 degrees C) and place rack in center of oven.  Butter and line the bottom of an 8 inch (23 cm) cake pan with parchment paper. 

In your electric mixer beat the eggs and sugar on high speed for about five minutes, or until they are thick, fluffy and light colored (when you slowly raise the beaters the batter will fall back into the bowl in a slow ribbon).  At this point beat in the vanilla extract.  In a small bowl whisk together the flour and salt.  Sift 1/2 of the flour over the batter and gently fold through with a rubber spatula or whisk.  Sift the remaining flour over the batter and fold in.  Whisk about 1/2 cup of the batter into the melted butter (to lighten it) and then gently fold the butter mixture back into the rest of the batter.  Pour immediately into the prepared pan and bake for about 25 minutes or until springy to the touch.  (A toothpick inserted in the middle will come out clean.)  Remove from oven and place on a wire rack to cool.  Run a spatula or sharp knife around the inside of the pan and then invert the cake onto a wire rack.  Remove parchment paper.  Set aside. (The cake can be made a day or two in advance. )

Strawberry Cream. Chill your mixing bowl and beaters in the freezer for about 15 minutes.  Meanwhile, in a small measuring cup stir together the gelatin and 1/4 cup of the strawberry puree.  Let this mixture sit for 5 minutes and then microwave for a few seconds to dissolve the gelatin.  Once the gelatin has dissolved, stir the gelatin mixture into the remaining 1/2 cup (120 ml) of puree.  Set aside while you whip the cream.

Beat the cream until soft peaks form and then add the puree mixture.  Continue to beat the cream until stiff peaks form.  Taste and fold in more sugar, if needed.. 

To assemble the Charlotte:  Cut a 3/4 inch (2 cm) layer from your sponge cake.  (Wrap and freeze the rest of the cake for another use.)  Place the cake layer on the bottom of an 8 inch (23 cm) springform pan.  Spread 1/4 cup of strawberry puree over the top of the sponge cake.  Halve the strawberries and fit them, snugly,  on top of the cake with the cut sides facing the outside edge of the pan.  Fill the center of the cake with the the strawberry whipped cream.  Smooth the top, cover loosely with plastic wrap, and chill for about 2-3 hours so the cream has time to set.  (The charlotte can be made up to this point and refrigerated for a day before serving.)

To unmold and serve: Several hours before serving, gently remove the sides of the springform pan.  Heat the apricot preserves in a small saucepan over low heat until barely warmed.  Then, using a pastry brush, glaze the cut surfaces of the strawberries and the outside edge of the cake.  Cover and refrigerate until serving time.  If desired, decorate the top of the cake with a whole strawberry. 

Serves 8-10