01 - Preheat the oven to 350°F. Line the bottom of a 9-inch springform pan with parchment paper.
02 - Beat eggs and sugar with an electric mixer until pale and tripled in volume (about 5 minutes). Gently fold in flour, salt, and vanilla extract until just combined. Pour into the pan and bake for 12-15 minutes, or until a toothpick inserted in the center comes out clean. Cool completely in the pan.
03 - Sprinkle gelatin over 3 tbsp cold water and let bloom for 5 minutes. Gently heat bloomed gelatin until dissolved (do not boil). Blend mango puree, sugar, and lemon juice until smooth. Stir in dissolved gelatin. Whip heavy cream to soft peaks and gently fold into the mango mixture until smooth.
04 - Pour the mousse over the cooled sponge base, smoothing the top. Refrigerate for at least 2 hours until set.
05 - Bloom gelatin in 2 tbsp cold water. Gently heat until dissolved. Mix mango puree, lemon juice, and sugar in a bowl, then stir in dissolved gelatin. Let cool to room temperature, then pour over the set mousse layer.
06 - Chill for at least 2 more hours, or until the glaze is firm. Carefully run a knife around the edge of the pan and remove the cake. Decorate with fresh mango slices and mint leaves if desired. Slice and serve chilled.