Place turkey, carrots, spinach, brown rice, oil, and raw egg in a large bowl.
Mix thoroughly to combine.
Pat 1/2 the mixture into a greased and waxed-paper-lined 9 inch round cake pan.
Layer the hard cooked egg slices over the mixture, then top with the remaining meat mixture.
Bake in a preheated 350°F oven for 45 to 50 minutes or until done.
Remove from oven and let rest in pan for 5 minutes.
Using a large spatula, remove from pan, draining off any grease, and allow to cool on a platter for 15 minutes before frosting and serving.
*This recipe makes 1 cake layer.*
**To make a layer cake, double the recipe and use two 9 inch cake pans. When cake layers are baked and cooled, place 1 layer on plate. Spread with about 2 cups mashed potatoes, then place other cake layer on top of mashed potato filling. Using a pastry bag with a large star tip, make mashed potato rosettes on top of cake if desired.**