Peel and chop up your sweet potato. Put it in a saucepan with a bit of water and cook until tender.
If you processed your own pumpkin and were keeping it frozen like I do, you probably want to defrost it now. Better yet, throw the frozen chunks in with the sweet potatos and kill two birds with one stone.
Once your sweet potato is soft, mash it up and combine it with the pumpkin puree.
Add sugar, cinnamon, salt, ginger, nutmeg, and cloves. Stir well.
Beat your egg(s) and add to the mixture, along with your milk. If your sweet potato / pumpkin mix is still warm enough, you can chop up the 1/4 cup of butter and melt it in with everything. If not, then melt the butter in the microwave, then add it to the mixture.
Add the rum! Mix everything together well.
Pour your mixture into 1-2 casserole dishes. I use varying amounts of sweet potato and pumpkin, so it often exceeds one 8x8 dish.