Preparation

1. Prepare a flat 18cm (7") disK of pâte sucrée. The ingredient amounts listed above will make two disks of this size; you can divide the dough in half and freeze the portion you’re not going to use.
2. Bake one 18cm (7") Sponge Cake Viennoise according to that recipe. Slice the cake into three layers and set aside.
3. Wash and hull strawberries, then dry thoroughly.
4. Begin preparing the gelatin for the strawberry gelatin and mousse in two separate small bowls or cups; put 2 and 2½ tablespoons of water in each bowl, respectively, then sprinkle the gelatin into the water and set aside.
5. Prepare syrup; mix water and sugar and microwave until hot. Stir until completely dissolved, then let cool. Stir in strawberry liqueur (or other fruit liqueur, such as Kirschwasser) and set aside.
6. Keep heavy cream chilled.

Directions

1. Make strawberry liquid for the gelatin.
   
   1. Put the strawberries, sugar, and water for the gelatin in a saucepan and simmer over low heat until the water turns red.
   2. Strain the liquid through cheesecloth and let cool. Set the strawberries aside for the mousse.
2. Make the strawberry mousse.
   
   1. Roughly slice 150g (5 oz.) of strawberries plus the pale strawberries leftover from the gelatin. Pour balsamic vinegar over the slices, stir to coat, and leave in a bowl to marinate for about 30 minutes.
   2. Take another 100g (3.5 oz.) of strawberries, cut them in half, and slice thinly.
   3. Pour the marinated strawberries and any liquid into a food processor and purée.
   4. Pour the heavy cream into a large bowl and whip until thick enough that cream dribbled from the beater briefly leaves a trail, but is not stiff.
   5. Microwave the prepared 6g of gelatin until it turns to liquid, then add to food processor and mix.
   6. Take the sliced strawberries from 2 and the strawberry purée from 5 and add them to the whipped cream, then stir until mixed.
3. Assemble cake.
   
   1. Warm enough strawberry jam to coat one surface of the pâte sucrée disk in the microwave to soften it, then coat the top of the tart. Place a cake-forming ring onto the plate the cake will be served on (if the ring you’re using is adjustable, size it slightly large than the tart base). Lay the base in the ring jam-side up.
   2. Lay the first layer of the sponge cake on top of the tart base, then dab on one third of the syrup.
   3. Pour one third of the mousse onto the sponge cake and spread smooth with a spatula. Make sure the mousse fills the gap between the edge of the ring and the sponge.
   4. Lay the second layer of sponge cake onto the mousse and press down lightly. Dab half the remaining syrup onto the cake. Pour half the remaining mousse on top, again spreading smooth and pushing it down to fill the gap around the edges.
   5. Lay the top layer of sponge cake on top, press down lightly, and dab with remaining syrup. Pour on remaining mousse and spread evenly; make sure there’s at least 5mm (¼") left at the top of the ring for the gelatin.
   6. Chill for about two hours in the refrigerator to set.
4. Make strawberry gelatin.
   
   1. Once the mousse has set, begin making the gelatin. Warm the 5g portion of prepared gelatin in the microwave to liquify; stir the gelatin and lemon juice into the strained strawberry liquid.
5. Finish cake.
   
   1. Slice the strawberries reserved for decoration into 3mm (eighth-inch) slices and arrange in a decorative pattern on the top of the chilled cake.
   2. Gently spoon the gelatin liquid on top of the cake in a layer to cover the strawberries, being careful not to make any bubbles.
   3. Chill in the refrigerator for an hour to set the gelatin, and the cake is complete.