Started off by making a single block with the rectangle tool and filling with suitable shade of brown. To give the chunky block feel a Bevel and Emboss was applied.
The individual blocks were merged together using Merge Visible ⌘E whist holding down ⌥ to make a copy.
To add a bit of visual interest the top right corner was selected with the Polygon Lasso Tool and slightly pulled away giving the effect of broken piece of chocolate. A drop shadow was also added to give more depth.
What we end up with is nice simple graphic which can pass for a chocolate bar. Now for the wrapper. We start by making a rectangle covering the lower half of the bar,giving it a suitable cover. The same Bevel and Emboss is used to give it form.
Starting with a rectange selection, filled with diamond gradient in difference mode. I dragged acrossed the selected area many time until I got the image in the top leftNext I applied FIlter > Stylize > Emboss with the above settings. The result looks like crumple paper. The select was turned into a brush using Edit > Define Brush Preset and the following setting applied to the brushThe brush was used in difference mode to randomly cover the whole layer, and a selection made as backdrop to the chocolate
Start with a new document (600x600px) I used the gradient tool in with the settings pictured below
Clicking randomly producing this rather psychedelic result. Then changing linear mode and dragging diagonally from the top right initially to produce the result to the left.The next step adds filters to give a gooey texture. The filters were applied in the order shown below.
The filters have these settings: