• Step 1: In a small saucepan, combine the raspberries, 1/4 cup of the sugar, and the water. Cook over medium heat, stirring occasionally, until the raspberries have broken down and the mixture has thickened, about 10 minutes. Remove from heat and let cool completely.
• Step 2: In a small bowl, sprinkle the gelatin over 2 tablespoons of cold water and let stand for 5 minutes to bloom.
• Step 3: In a medium bowl, beat the egg whites with an electric mixer until foamy. Gradually add the remaining 3/4 cup of sugar and beat until stiff, glossy peaks form.
• Step 4: In a separate bowl, whip the heavy cream until it holds soft peaks.
• Step 5: Reheat the raspberry mixture over low heat and stir in the bloomed gelatin until dissolved. Remove from heat and let cool slightly.
• Step 6: Fold the whipped cream into the raspberry mixture, then gently fold in the whipped egg whites until well combined.
• Step 7: Place the sponge cake on a serving platter or cake board. Spread the raspberry jam or preserves over the top. Carefully pour the raspberry mousse over the cake, smoothing the top with a spatula.
• Step 8: Refrigerate the cake for at least 4 hours or up to 2 days.
• Step 9: In a small saucepan, melt the white chocolate chips with the remaining 1/4 cup water over low heat, stirring constantly until smooth. Let cool slightly, then pour the glaze over the chilled cake, ensuring it drips down the sides. Refrigerate the cake for an additional 30 minutes to set the glaze.
• Step 10: Serve chilled. Garnish with fresh raspberries or a dusting of powdered sugar, if desired.