Begin by crushing the chocolate sandwich cookies into fine crumbs using a food processor or a resealable plastic bag and a rolling pin. Combine the cookie crumbs with melted unsalted butter until well mixed. Firmly press the mixture into the bottom of your molds, creating an even layer. Place in the freezer for 15 minutes to set.

In a saucepan, combine blackberries, sugar, and water. Heat over medium heat for about 5-7 minutes until the berries have softened. Blend the mixture until smooth, then strain through a sieve to remove seeds. Return the purée to the saucepan and stir in bloomed gelatin mixed with lemon juice until fully dissolved.

In a separate bowl, whip heavy cream until soft peaks form. Gently fold the whipped cream and vanilla extract into the blackberry mixture using a spatula.

Remove the crust from the freezer and pour the blackberry mousse mixture over the crust, smoothing the top with a spatula. Cover with plastic wrap and refrigerate for at least 4 hours.

In a small saucepan, heat heavy cream until it begins to simmer. Pour the hot cream over white chocolate chips and let sit for a minute. Stir until smooth and allow it to cool slightly.

Once the mousse cakes are set, remove them from the molds. Pour the slightly cooled glaze over the top, letting it drip down the sides. Garnish with fresh blackberries and edible flowers before serving.