Fattening others

Peanutbutter, and whole milk can work wonders. As well as using olive oil (healthy fats, but fatty nonetheless), since it has 14g of fat per tbsp. Get some sweet potatoes, and/or Yukon potatoes, toss em in the oven then add any combo of the following butter, sour cream, cheese, olive oil, bacon bits

I've mentioned this before, but there are countless instant dishes at the store that take milk and butter: macaroni & cheese, flavored rice, risotto, tuna/chicken helper, lipton noodle packets, mashed potatoes, etc. etc.

Sub heavy cream for the milk. And double the butter. It always tastes better than the standard prep and it becomes a calorie heaping gainer's dish.

Get creative; add cream cheese to your macaroni & cheese (it's amazing!). Add cheese, to well, virtually everything for a couple hundred easy calories. This is also not sugar centric, leading to diabetes issues.