Preheat oven to 360º F/ 180º C. Line two 7 inch/ 18 cm cake pans with circles of parchment paper. Grease very well the pans inside.
In a medium bowl combine the flour and baking powder. Mix well and set aside.
Use a blender or a food processor to shred the spinach finely.
In a large mixing bowl beat the eggs and the sugar with an electric mixer for 4-5 minutes, until fluffy and pale.
Gradually add oil, vanilla and milk and beat after each until combined.
Using a rubber spatula or the paddle attachment of a stand mixer, fold the spinach into the batter. At the end gradually add the flour mixture, mixing at a low speed just until combined (or gently with a spatula).
Divide the batter between the two pans.
Bake for about 40 minutes or until a toothpick, inserted in the centre, comes out clean. Let the cakes cool until room temperature, before cutting and assembling them.
Combine all ingredients in a large mixing bowl. Make sure the mascarpone and the cream are cold.
Beat with an electric mixer at high speed just until fluffy. Do not overbeat!
Cut horizontally the cake bases with a long serrated knife. Place one half on a serving plate and spread generously some frosting on top. Continue the process until finishing all cake bases.
Frost the cake all around with the remaining frosting: it should be about ⅓ of the whole quantity.
Refrigerate the cake at least 4-6 hours before serving it.
Decorate with fresh fruits.
Store the cake for 2-3 days in the fridge.
The spinach doesn't need to be exactly pureed, as long as it is very finely shredded (see video).
Instead of baby spinach you can use regular one, as long as any hard stems are thoroughly removed.
Ideally refrigerate the cake bases overnight, covered with plastic wrap. This will help for easier cutting as the layers are crumbly.
Always reserve for the top of the cake a layer that has been on the bottom of the pan during baking!