If you go to the Food Network's website you will find a petit fours recipe under "Anne Thornton". It sounds good, but also sounds like a LOT of work.
If I were making them, and didn't want to spend quite that much time doing it, I would do it an easier way. How about making a dense cake, like a poundcake? You can make it from a mix. Bake the cake the day before you plan to use it. If you try to cut the cake into small shapes the same day you bake it, it will be too crumbly and difficult to work with.
So -- bake a poundcake in a 13x9x2 baking pan. Remove from pan. Let cool overnight.
If you wish, you can split the cake and spread raspberry jam between the layers, and you can roll out some marzipan into a thin sheet and put that between the layers also.
Trim the edges from the cake, then cut the cake into small diamond shapes, or any shape desired.
Place the cut out shapes on a rack over a cookie sheet. Take a couple of tubs of ready made frosting and GENTLY heat it for a few seconds at a time in the microwave. Stir every 5-10 seconds or so, until a pourable (but not too watery) consistency is achieved. Pour (or spoon) the melted icing over the petit fours. Depending on how thin the icing is, this may take more than one coat. Let set between coats.
After the icing has set, decorate the cakes with tiny flowers, drizzles of contrasting icing, or anything that you find pretty. If it's hot or humid, you may want to put the cakes in the refrigerator for a few minutes to harden.
Hope this helps. Have fun if you make them!