I made this image a while back, but will give a little how-to here. It’s a combination of two shots that were shot with the exact same lighting to make it easy to combine them. They were lit by one snooted light from the left with the subject sitting on a white piece of paper. The snoot creates a small spot of light making the subject stand out against the black background, this works especially well with a white subject. To cut down the shadow in the cup cake I placed a reflector to the right.
I could not find a cup I liked but did find a milk can that had an ear that I liked so I used it. The saucer for it was a bit big for the cup cake but I was confident it would work, so I went with it.
Original image of milk can on saucer
Original image of cup cake on saucer
I used two parts out of the can shot: the ear and the saucer. The can was much bigger than what would be covered by the cup cake so I painted the top away with some black, another advantage of a simple background. I did not really like how the light fell off to the bottom of the image so I added a layer in Normal blend mode and painted some white in it. Using a feathered brush it easily melded with the original
Next I added the cut out cup cake on a new layer, the cut out was not too hard because most of the edges were pretty straight and where they were not the contrast with the background was high. I kept the reflection of the cup cake in the saucer to make the combination more believable. When combining two objects it is always important to keep their interaction intact, or create it if it is not in the original images. You can see some problems in the the combined images, these will be tackled one at a time.
Saucer with cup cake
The shadow on the saucer from the can and the one from the cake did not line up nicely so I copied the shadow from the can to a new layer and stretched it a bit to make it line up with the bottom of the cup cake. A layer mask makes it blend in nicely with the underlying one.
Now it was time to add the ear. This was harder than I expected, it had to be sized down and I had to fiddle around with it a lot to have it look natural. I think if I had used a real cup instead of a milk can this step would have been much easier.
Even though the shadows from the milk can were from a bigger object that how I am presenting the cup cake the shadows looked just fine. Except the one in the ear. I wanted the ridges of the cup cake to be visible there, so I painted them in.
Shadow on ear edited
Lastly the reflection of the cup cake in the saucer was way to dark to be believable. I corrected this with a curves adjustment targeted to the reflection with a layer mask. Some feathering in the layer mask makes the effect blend in with the existing shadow on the right.
You can download a TIFF file with all the adjustment layers below to play with. It works nicely in PhotoShop CS 5 but I expect it to work in other versions and other editing software as well.