Prep the cake mold: Line a deep 8-inch (20 cm) round cake pan (at least 3 inches/7.5 cm deep), a springform pan, or a saucepan with straight sides with plastic wrap, being sure that the wrap has plenty of overhang.

Cut out the cake layers: Using a small serrated knife and the bottom of the cake mold as a guide, trace an 8-inch (20 cm) circle on the upper left-hand corner of the sheet. Trace another 8-inch (20 cm) circle on the lower right-hand corner of the sponge sheet. Carefully cut out the rounds with the knife and set aside. Use the bottom of the cake mold to trace a half-moon shape on the upper right-hand corner of the sheet, and then another one on the lower left-hand corner of the sheet, and cut these out. Finally, cut out a rectangle 8 inches (20 cm) long and 1 inch (2.5 cm) wide from the center of the sheet. You’ll piece these 3 scraps together to form a circle for the center layer of the cake.

Whip the cream: In a stand mixer fitted with the whisk (or in a large bowl using a handheld mixer), whip the heavy cream until stiff, about 3 minutes. Keep chilled until ready to build the cake.

Build the cake: Place one round cake layer in the bottom of the plastic wrap–lined pan. Dab ¼ cup (60 grams) of the tequila coconut soak onto the cake. Add ⅔ cup (160 grams) of the passion fruit curd and spread it evenly. Sprinkle ¼ cup (30 grams) of the coconut streusel on top. Spoon half of the whipped cream on top and gently smooth and press it out to the edges. Arrange the two half-moons and the rectangular piece on top to form a round, then add ¼ cup (60 grams) soak. Layer ⅔ cup (160 grams) curd, the remaining ¼ cup (30 grams) coconut streusel, and the other half of the whipped cream on top. Finally, place the second round on top to seal the cake shut, and brush the remaining ¼ cup (60 grams) soak on top. Securely wrap the entire cake form in plastic wrap and transfer to the refrigerator to rest for at least 8 hours (or longer) or to the freezer for at least 5 hours, or up to 3 days, so the flavors can meld.

Mix the passion fruit buttercream: After the cake has rested, it will be stable enough to be iced. In a stand mixer fitted with the whisk, whip the buttercream until smooth, about 2 minutes. Add the remaining passion fruit curd and whip until smooth, glossy, and thick, another 3 minutes.

Frost the cake: Invert the chilled cake onto a platter or a 10-inch (25 cm) cardboard cake round. Remove the cake form, then peel off the plastic wrap. Use an offset spatula to dollop half of the whipped buttercream all over the surface of the cake. Spread the buttercream all the way to the edges of the cake. Dab the remaining buttercream along the sides of the cake, smoothing each dab to touch the one before, until none of the cake is visible. Once the sides of the cake are roughly covered in buttercream, run the offset spatula along the surface again to smooth.

Decorate the cake: Scatter the flower petals or leaves over the surface of the cake, letting them fall in a natural way. The cake can sit out in a cool environment for 5 to 6 hours, but on a hot day, beware of greasy-looking icing. And the cake tastes best if the slices are still slightly chilled.