Make a simple syrup by combining 1 cup of water and the sugar in a small saucepan over medium heat. Stir until the sugar dissolves, then bring the mixture to a boil. Once it boils, remove the pan from the heat, then stir in the optional framboise, if using. Let it cool to room temperature while you prepare the cake. Have your room temperature buttercream and room temperature raspberry jam ready.
Flip the cake upside-down onto a cutting board and peel off the piece of parchment. Cut the cake into six rectangles by cutting the cake across the middle lengthwise, then cutting it into thirds widthwise. Use a long serrated knife to carefully cut each rectangle into two thin layers (like you would cut a cake into layers) so that you’re left with 12 thin rectangles.
Brush one rectangle with the simple syrup mixture. Dollop on a spoonful of raspberry jam, and spread it in a thin layer over the cake. You want enough jam so that the flavor comes through, but not so much that the cake is unstable.
Top the jam with another cake slice, and brush it with more simple syrup. Top this cake layer with a thin layer of tangerine buttercream, about the same height as one of the cake layers.
Brush one more cake layer with simple syrup, then place it, syrup side-down, on top of the buttercream. You should now have a 3-tiered rectangle of cake. Set it aside and repeat this process with the remaining cake layers, until you have four rectangles of assembled cake.
Divide the marzipan in four pieces and roll each into a very thin layer. Brush the top of one of the rectangles with a bit of simple syrup, and press the marzipan on top. Trim the edges so the marzipan is flush with the sides of the cake, and repeat until all of the cake rectangles are covered with marzipan. The marzipan is technically optional, but it helps give your dipped cakes a clean look on top. Refrigerate the tray to firm up the cake rectangles, for about 45 minutes.
Once firm, use an egg cookie cutter to cut egg shapes out of your cake. If the cake layers are taller than the cutter, try pressing the cutter down until it is flush with the top of the cake, then using a paring knife to trim around the bottom—this prevents the top of your egg petit fours from getting dented or smashed when you try to press the cutter to the bottom of the cake.
Place the eggs on a baking sheet and freeze them until firm, about 1-2 hours. The eggs should be very hard before you dip them.
If you want to make your fondant different colors, divide it up into smaller bowls and work with one portion at a time. Warm up your fondant in the microwave until it is very warm and very fluid—it should readily pour from a spoon. Add a drop of food coloring and stir it in, then adjust the color and add another drop or two if desired. You will need to warm up the fondant fairly frequently during the dipping, so it’s easiest if you work near the microwave.
Take the tray of cake from the freezer. Press a wooden barbeque skewer through the bottom of one of the pieces, until it is firmly in the middle but not poking through the top.
Dip the top of the cake into the fondant at a 45-degree angle and swirl it around. Use a spoon to pour fondant on the sides of the cake as you twirl it. Remove it from the fondant, let the excess drip back into the bowl, and use a spoon to touch up any areas that were missing fondant.
Take a fork and put it under the piece of cake, twist the skewer to remove it so the cake is resting on the fork, then gently set the cake onto a wire cooling rack to set.
Repeat until all of the pieces of cake are dipped. If the fondant gets too thick, re-warm it in brief intervals in the microwave. Once the fondant is set, use a sharp knife to carefully loosen them from the wire rack.
To add the speckled appearance, mix the cocoa and 2 tbsp warm water in a small bowl until the cocoa powder dissolves. Dip a small paintbrush in the cocoa mixture, then flick it against your finger so that the cocoa splatters. (I recommend doing this step over a sink for easy clean-up.) Continue to dip and flick the brush until the petit fours are as speckled as you want.
For the best taste and texture, enjoy these petit fours at room temperature. Store extra petit fours in an airtight container in the refrigerator for up to two weeks.