Making the patties with just the meat does it for me.
I can see adding an egg with double the meat but even then .....
All that flour ? You should let the meat speak for itself. The burger will not fall apart if you don't add the flour or egg , is that the fear ?
Yes, there are also molds that can be used.
Roll out fondant , drape and fill mold , unmold , place on cake making sure the ends match .
Hand painted or airbrushed.
Molds cost about 10.00 - 20.00 a piece . Intricate designs cost more. There are 5-6 molds for that cake . They also used a stencil for the middle of the gold frame.