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