Preheat oven to 350°F. Prepare banana leaves.
BANANA LEAVES: Thaw frozen banana leaves. Wash before using. Wipe leaves dry. Pass banana leaf over an open flame (stove-top) 2-3 times to make the leaves more pliable. Hold the leaves using tongs to prevent burning your fingers. DO NOT BURN THE LEAVES.
Once leaves are flexible, use scissors to cut leaves into appropriate size to line mini pie tins or tart shells. Grease banana leaves with softened butter and set aside.
CAKE BATTER: In a large bowl, whisk together eggs, sugar, coconut milk, evaporated milk, and melted butter until smooth. Add grated cassava and grated fresh coconut. Season with salt. Fold until mixture is well combined.
Spoon about a rounded cup of mixture into each prepared mini pie tin (more if using a larger/wider tart shell). Spread mixture into an layer. Bake for 20-22 minutes until cake is almost set.
TOPPING: While cake is baking, prepare topping. In a small heavy-bottomed sauce pot, whisk together coconut cream, condensed milk, sugar, egg yolks, and butter. Set over medium heat. Stirring continuously, bring mixture to a boil. Reduce to a simmer and continue to stir until mixture has thickened.
Remove cakes from oven. Spread a thin layer of coconut cream topping over each cake. Remove to oven and cook for another 10-12 minutes until cakes are completely set. If desired, set up broiler for 30 seconds to gently caramelize sugar on topping. BE CAREFUL because banana leaves may flame and fire.
Cassava bibingka can be served warm, at room temperature, or chilled. Season with additional salt to make the cake taste "sweeter." Alternatively, baked cakes can be topped with grated salted hard cheese or salted duck eggs.