If you would like to make this into a four layer cake, double the frosting recipe. Slice each baked layer into two. Add the same amount of carrot cake jam to each layer as before, and frost like normal. If you'd like this to serve a larger crowd you can also double the cake recipe and bake this in three 10 inch cake pans and bake them for 35-40 minutes. You should still double the frosting and the carrot cake jam. This could also become a six layer cake, but then you would require even more frosting.