Separate 3 egg yolks and use 3 whole eggs. Add sugar and gently whisk until combined. In a saucepan, heat 1/2 cup sugar with a little water over medium heat until it turns a golden caramel color, then add a few drops of lemon juice. Quickly pour the caramel into the mold. Warm the milk on the stove, then slowly pour it into the eggs while gently whisking. Strain the mixture for a smooth texture. Add rum and vanilla extract. Preheat the oven to 320°F (160°C). Pour the mixture into the caramel-lined mold, place the mold in a water bath, and bake for about 30 minutes. The flan is done when a toothpick inserted comes out clean. Set aside the flan to use in the jelly layer.

Mix 25 grams agar powder with sugar. Bring 8 1/2 cups (2 liters) water to a boil, then gradually add the agar-sugar mixture, stirring gently until dissolved. Prepare food coloring and molds. Add 1 teaspoon sweetened condensed milk to each color, then pour in the jelly mixture, stir well, and pour into the flower molds to set.

Once the jelly in the flower molds has set slightly, remove the flowers from the molds. For the large heart-shaped mold, pour a thin layer of jelly into the bottom and let it set. Arrange a few flower petals on top, then place the flan in the center. Continue pouring layers of jelly mixed with coconut milk, then jelly with pandan flavor, letting each layer set before adding the next, until the mold is full.

Once the jelly is completely set, remove the cake from the mold and decorate with the flower petals as you like. You can create different styles of jelly cakes. This is a delicious, refreshing, and unique dessert, perfect for parties with its elegant decoration.