Make the crumb mixture: Place the 80 g of digestive biscuits into a sturdy plastic bag or between two sheets of parchment paper. Crush them into fine crumbs using a rolling pin. Transfer the crumbs to a medium bowl. Pour in the 40 g of melted unsalted butter and mix with a fork or spatula until all the crumbs are evenly coated and resemble wet sand.

Form the base: Line the bottom of a 6-inch springform cake mold with a circle of parchment paper. Pour the buttery crumb mixture into the mold. Use the bottom of a flat glass or a measuring cup to press the crumbs down firmly and evenly into the bottom of the pan. Set the base aside while you prepare the mousse.

Prepare the mango puree: Place the 400 g of fresh mango flesh in a food processor or blender. Blend until it is completely smooth, with no lumps or fibrous bits. Measure out 300 g of this puree for the mousse. (The remaining 50 g will be used for the mirror glaze.)

Heat the puree: Pour the 300 g of mango puree into a small saucepan. Add the 40 g of granulated sugar. Heat the mixture over low flame, stirring constantly, just until the sugar has completely dissolved. Remove from the heat immediately and set aside to cool until it reaches 55°C (131°F).

Bloom and melt the gelatin: While the puree is cooling, place the 15 g of gelatin sheets in a bowl of cold water. Let them soak for 5-10 minutes until they are fully softened. Once the puree has cooled to 55°C, remove the gelatin sheets from the water, squeeze firmly to remove any excess water, and add them to the warm puree. Stir until the gelatin is completely dissolved.

Whip the cream: In a separate, clean mixing bowl, add the 220 g of chilled heavy cream. Using a hand mixer or a whisk, whip the cream until it reaches a thick, yogurt-like consistency. It should hold a soft trail when drizzled but still be fluid, not stiff.

Combine to make the mousse: Pour the mango-gelatin mixture into the whipped cream. Use a silicone spatula to gently fold everything together until the mixture is uniform and no streaks of cream remain. Be careful not to overmix, as you want to keep the mousse light and airy.

Assemble the first layer: Pour the mango mousse onto the prepared biscuit base. Gently tap the mold on the counter a few times to release any large air bubbles. Place the mold in the freezer for 20 minutes to allow the mousse layer to set just enough to support the next layer.

Make the glaze: Take the reserved 50 g of mango puree and pour it into a small saucepan. Add the 50 g of water and the 5 g of granulated sugar. Heat over low flame, stirring, just until the sugar has dissolved. Remove from the heat and let it cool until it reaches 55°C (131°F).

Bloom and melt the glaze gelatin: Soak the 3 g of gelatin sheets in cold water until soft. Squeeze out the excess water, then add them to the 55°C glaze mixture. Stir until the gelatin is completely dissolved. Allow the glaze to cool until it is just lukewarm to the touch.

Add the final layer: Remove the mold from the freezer. Gently and slowly pour the cooled mango glaze over the top of the semi-set mousse. Give the mold a gentle swirl to ensure the glaze is level. Return the cake to the refrigerator and let it chill for at least 6 hours, but preferably overnight, to fully set.

Unmold and serve: Once the cake is completely firm, remove it from the refrigerator. To unmold, you can wrap a warm, damp towel around the outside of the springform pan for a few seconds to loosen the edges, then carefully release the clasp. Transfer the cake to a serving plate. Decorate with fresh mango slices, blueberries, mint leaves, or edible flowers as desired.