I feed fudge porridge for breakfast, usually only for a couple of days in a row then take a few days off so she doesn't get sick of it.
I feed it whichever way she seems to prefer it at the time (constantly changing her mind!). Make it with boiling water and mix until stodgy, either serve as is or with mashed pear, Apple, or fudges favourites are banana and blueberry. I make a heaped teaspoon sized serving as that's all she'll eat in one sitting. On occasion il scatter some dry oats through her oat hay (another good thing to feed a skinny pig) but be careful to only give a pinch of dry oats Incase is causes a bloated tummy, soaked oats are safer.
Try not overdo the fruit side Incase you cause diarrhoea. Corn on the cob, pea flakes and oat hay are great ways of getting some extra calories in them.
Fudge is 7 years 7 months and a cracking 1030g currently, only 20g below her prime weight despite all her health complications. A balanced diet with the right amount of higher calorie foods seems to keep the weight ticking over for her.