To make the devil's food cake: Preheat oven to 350 degrees F and line two jelly roll pans with parchment. Combine the sugar, flour, cocoa powder, baking powder, baking soda, and salt together in a large bowl and whisk until combined, set aside. Whisk together, eggs, milk, oil and vanilla until well combined. Add the egg mixture to the dry ingredients and whisk until smooth. Slowly add the hot coffee and rum to the batter and whisk until smooth, about 2 minutes. The batter will be quite runny. Pour into prepared pans and bake the layers for about 20 minutes or until set. Cool on a rack. Can be made and refrigerated the day before. Cut the devil's food cake with a heart cookie cutter. Depending on the size of your cutter this will get you about 12 2-layer cakes per sheet.
To make the cream: Whip the heavy cream until soft peaks, add the raspberry preserves and continue whipping until stiff peaks. Fill a pastry bag, fitted with a round pastry tip and pipe the cream on half of the heart shaped cakes. Top the cream with another layer of cake. Cover the cake with plastic wrap and refrigerate while you make the ganache.
To make the ganache: Heat the strained apricot preserves in a saucepan over medium-low heat until melted. Add the cream, milk and corn syrup and heat just to simmer. Remove from the heat. Add all the chopped chocolate, swirl the pot to make sure the chocolate is completely covered by the cream. Let sit for about 3 minutes and then gently whisk until smooth. Pour about 1 cup of the hot ganache into a shallow dish and refrigerate for 10 minutes or until slightly firm, but still spreadable. Leave the remainder of the ganache in the pot to keep it pourable. With a small spatula, spread the refrigerated ganache over the sides of the cakes. The goal is to fill the gap between the layers of cake and make them smooth. We want a smooth surface so that when you pour the ganache over the cakes you will not have any bumps.
To pour the ganache on the cakes: Set the cakes on a cooling rack over a sheet pan lined with parchment. You want to do this to catch all of the dripping chocolate. Slowly pour the ganache over the cake, starting in the middle and working outward. Be sure to check all the sides as you go. There will be a lot pooled up on the parchment, but you can scrape that up and melt to use again. If your ganache starts to get too thick, return the pot to the stove and heat on very low heat, just for a few seconds. Allow the cakes to set at room temperature for about 20 minutes. If you need to refrigerate them, they will lose their shine. Once you return them to room temperature the shine will come back. To make the blackberry coulis: Cook the berries, sugar and liqueur in a saucepan over low heat at a simmer for about 5 minutes. Use an immersion blender to puree the berries. Strain through a chinois or fine mesh strainer. You can find edible roses at some grocery stores or ask your local florist.