How to refer to this method of mixing solids?
I think the closest term would be recrystalisation though this is normally used to dissolve one component (the desired one) to allow the removal of impurities, so I would be hesitant to use it but it is used here to describe the rocket candy example you used: http://www.jamesyawn.net/rcandy/index.htm

With regards to your second example, baking a cake is actually a series of interesting and complex chemical reactions and structural changes. The New Zealand institute of chemistry wrote a nice summary of the chemistry of baking that can be found here: http://nzic.org.nz/ChemProcesses/food/6D.pdf

Hope that helps