First, peel all 15 saba bananas and place them in a large pot. Fill the pot with enough water to cover all the bananas. Turn your stove to high heat (180°C/350°F) and bring the water to a boil.
Once boiling, lower the heat to medium (150°C/300°F) and cook the bananas for 12-15 minutes. You can check if they're done by poking with a fork - it should go through easily. When they're tender, drain all the water and let the bananas cool slightly.
Place the cooked bananas in your wooden mortar (lusong) or large bowl if using a potato masher. Pound or mash the bananas until completely smooth with no lumps. Take your time with this step to ensure a silky texture.
Add the freshly grated coconut to your mashed bananas. If using the traditional method, continue pounding until well combined. Next, add the brown sugar and vanilla extract. Keep pounding or mixing until everything is evenly combined and smooth.
If you're using banana leaves for serving, quickly pass them over a flame or hot stove to make them soft and shiny. Wipe them clean with a damp cloth. This step is optional but adds a wonderful traditional aroma.
Transfer your mixture to a serving plate. Shape it into either a dome or flatten it to cut into squares later. Using a brush or spoon, generously coat the top with softened butter or margarine. If you prepared banana leaves, place them on your serving plate first, then add the linupak.
Finally, cut your linupak into squares or diamond shapes. Serve while still warm for the best experience. You can enjoy it at room temperature too, but warm linupak has the most comforting texture and aroma.
Remember to keep your hands slightly wet when shaping the mixture to prevent sticking. The whole process takes about 35 minutes, and the recipe serves 8-10 people.