Almonds, cashews, walnuts, etc are very high in calories and a good source of healthy fat. Adding a handful of almonds or a tablespoon of extra virgin olive oil to meals is a great way to up calories. You could also try adding ground flax seeds to your meals for some additional fibre, fat and a little protein. Pasta (perogies are great for packing in the cals) lean ground beef and cheese are good choices too. You can also make a pretty calorie dense/tasty bowl of oatmeal by adding some peanut butter or walnuts/cashews, berries, whey protein, banana, etc. PB and J sandwiches pack in the calories pretty well too.