The day before, rehydrate the gelatin in cold water. Heat 17 fl oz of water with the kirsch and grenadine. Add the drained gelatin and whisk. Let it cool completely.
Wash and hull the ciflorette strawberries. Cut them into small pieces and place them at the bottom of a giant trifle bowl, 6.3 to 7 inches in diameter, or a deep, straight-sided, transparent bowl. Pour the gelatin syrup over the strawberries and refrigerate overnight to allow the jelly to set.
The next day, trim the outer crust from the sponge cake to match the diameter of the trifle bowl.
Place the heavy cream in a mixing bowl and chill it in the freezer for 10 minutes. Whip the cream with the mascarpone using a mixer. At the end, gently fold in the sifted powdered sugar using a spatula.
Wash the Charlotte strawberries and cut them in half. Pour a quarter of the whipped cream into the trifle bowl, then place the sponge cake disk and pour more cream on top. Arrange the largest strawberry halves, cut side facing the glass, around the inside edge of the trifle bowl. Fill the center with the remaining cream.
Add the remaining cream, including any trimmings from the sponge cake. Refrigerate for at least 2 hours.
Wash, dry, and arrange the Mara des Bois strawberries on top of the trifle just before serving. Sprinkle with crumbled freeze-dried strawberries if desired. Serve immediately.