I baked up 3-8" round rich chocolate cakes (family recipe). After cooling I leveled them (except for the top layer), stacked while filling with vanilla butter cream, then dirty iced the whole cake. I saran wrapped then foil wrapped the cake and popped it in the freezer over night.
Once it was solid I removed it then started carving out the shape of my cat. I did not carve the tail and ears and just did a basic shape for the face. Details to the face (shape of muzzle, eye sockets, ears) were then added using candy "Clay" that I made (Wilton recipe with their Candy Melts, VERY simple). The candy clay dried pretty hard almost instantly due to the cake being so cold. So I had to work fast, if there were lumps I just used a knife to cut/smooth them out, carefully don't want to pull apart the cake.
After that I rolled out plain white fondant (I make my own Marshmallow fondant) and covered the cat completely. Took more fondant and rolled it into a log, and worked with it till I got the desired thickness and length to match my own cats tail! Kitty had a tail!
I let this air dry, it took approximately 7 hours for it to dry. I then took a smooth blade knife and began the long process of scratching hair (since I don't have fondant tools and a fork didn't work right for me.) After the hair was all scratched in, I mixed a little Wilton Gel Colors with a very little (like one or two drops depending on how much gel color) bit of extract (flavor not too important but it was butter extract or you can just use water). With food safe paint brushes I began the, also very long process of, painting the cat.