Take everything you ever learned about proper caloric intake, portion control, and limiting fats, do a 180 and that's a CF diet. Eat a lot, eat often, eat butter, cream, milk, and anything else fattening.
My mom used to make this stuff for me and my brother. Its perfect CFer food. It has lots of calories, tastes great even when you're sick and its easy to make.
What you'll need:
A large container of cottage cheese
A tub of Cool Whip
A can of pineapple (I like tidbits but you can use anything except rings for this)
A packet of your favorite flavor of Jello
A large bowl with a lid
A big spoon for stirring
Let your Cool Whip thaw out so its not a solid lump. Drain the juice off of your pineapple. Dump all of your cottage cheese, cool whip, and pineapple in your bowl. Throw in some marshmellows, whatever will fit. Stir that shit up! When its all evenly mixed smooth out the top. Cut just the corner off of your packet of Jello. Sprinkle it over the top of your slop. You won't need anywhere near the whole packet. You can save it for your next batch if you want to. Eat up!
This makes quite a lot of stuff, so you can halve it if you want to. I don't, it keeps just fine in the fridge for a couple of days so I can finish it off before it goes south.