This recipe is a great recipe for a moist and spicy crumb cake. I have made half the recipe (see below) in a 9 1/2" x 6 1/2" x 2" pan.
For the mashed sweet potatoes, 2 large sweet potatoes (or 1 pound of sweet potatoes) should yield 1 cup of mashed sweet potatoes.
My preferred method of cooking sweet potatoes is to steam the whole sweet potatoes (unpeeled). Place steamer basket in a pot with about 1 to 2 inches of water. Place whole sweet potatoes in basket and bring to boil. Cook for about 20 to 40 minutes depending on the size. Check every so often to be sure there is still water; add more if needed. Prick with a fork to check if done. Remove from basket and cool until able to handle. Slice in half lengthwise, scoop sweet potato out from skin into bowl. Mash with electric mixer.