Have you considered including coconut oil and coconut milk? These two products are fantastic to add calories and keep it healthy.
Coconut milk is absolutely delicious, and very versatile. One of my favorites is coconut milk soup (picked a random recipe for it: Cooks.com - Recipe - Thai Chicken And Coconut Milk Soup (Tom Ka Gai)
). I cook Thai quite a bit for fun, and I'd be happy to offer more recipes if you'd like.
Almond butter is also a great solution, and paleo friendly.