Separate the egg yolks and egg white. In a bowl, whisk the egg yolk, vegetable oil, water, evaporated milk, and sugar until well incorporated.
In another bowl, whisk flour, baking powder and salt before whisking. Gradually combine the wet and dry ingredients.
Next, make the meringue by beating the egg white using a hand-held mixer at low speed. Add the cream of tartar and gradually add the sugar as you continue to beat until stiff peaks form.
Fold ⅓ of the meringue into the batter then immediately add the remaining egg mixture until well incorporated.
Grease the lyanera with melted butter. Fill it with batter up to ⅔ full. Steam for 15-18 minutes over low heat. Alternatively, bake at 160°C for 25-30 minutes with a water bath or bain marie.
Meanwhile, make the frosting, whip the pure cream while gradually add the sugar. Continue to whip until stiff peaks form. Set aside inside the refrigerator.
To make the chocolate ganache, combine chocolate melts and vegetable oil. Microwave for 30 seconds until melted.
To assemble and decorate, transfer the sponge cake in a container or plastic tub, pipe the frosting on the sides and top of the cake. Put 2 heaping tablespoon of cubed mangoes on top and drizzle with chocolate ganache.