Butter two 9 inch = 23 cm round cake pans and line the bottoms of the pans with parchment paper. Set aside.
In a mixing bowl sift together the flour, salt, and cocoa powder. Set aside.
With a hand mixer, beat the butter until soft about 2 minutes.
Add the sugar and beat until light and fluffy about 3 minutes.
Add the eggs, one at a time, beating well after each addition.
Scrape down the sides of the bowl.
Add the vanilla extract and beat until combined.
Whisk the heavy cream with the red food coloring.
With the mixer on low speed, alternately add the flour mixture and heavy cream mixture to the butter mixture, in small additions, beginning and ending with the flour.
Combine the vinegar and baking powder. Allow the mixture to fizz and then quickly fold into the cake batter.
Divide the batter evenly between the two prepared pans and smooth the tops with a spatula.
Bake in the center of the preheated oven for approximately 25 – 30 minutes, or until a toothpick inserted in the center of the cakes comes out clean.
Cool the cakes in their pans on a wire rack for 10 minutes.
Place a wire rack on top of the cake pan and invert, lifting off the pan.
Once the cakes have completely cooled, place the cake layers in the refrigerator for 1/2 an hour.
Cut hearts with the cookie cutters and place on a large plate.
Make the filling: In a hand mixer beat butter on low speed for 2 minutes then on high speed until light and fluff. Add cream cheese and mix until smooth. Add sugar gradually until fully incorporated and smooth. Add in the coconut flakes and mix with a spatula.
Pipe or spoon the filling on one of the hearts, top with the other half and keep in the fridge while you melt the white chocolate (freeze any leftover frosting).
In a bain marie melt the chocolate until runny. You should be able to drizzle it over the cakes with a fork.
Remove sandwiches from the fridge and drizzle chocolate.