Preheat your oven to 350°F (175°C) and line a 9-inch springform pan with parchment paper. In a large mixing bowl, whisk together the dry ingredients: cake flour, baking powder, baking soda, and salt. Blend in the wet ingredients—sugar, milk, neutral oil, and vanilla extract—stirring until smooth. Pour the batter into the prepared pan and bake for about 15 minutes, or until a toothpick comes out clean. Cool completely on a wire rack.

Bloom gelatin by sprinkling it over cold water and let it sit for about 5 minutes. Blend ripe mango chunks until smooth, reserving about 400 grams for the mango curd. Microwave the bloomed gelatin until fully dissolved, then mix it into the mango puree. Whip the cream until stiff peaks form; gently fold into the mango mixture. Pour the mousse over the cooled cake and smooth the top. Refrigerate for at least 2-3 hours to set.

In a saucepan, warm the reserved mango puree with granulated sugar, stirring until blended. Mix cornstarch with water; gradually stir this into the warm mango mixture. Continue stirring until thickened, about 3-5 minutes. Remove from heat, add butter, and stir until melted. Strain through a fine mesh sieve to remove lumps. Allow to cool slightly before spreading over the chilled mousse.

Pour the cooled mango curd over the set mango mousse, smooth it out. Cover with plastic wrap, pressing gently to prevent a skin. Chill in the refrigerator for at least 12 hours. When serving, carefully remove from the springform pan and slice into portions to showcase the layers.