well, speaking from someone who was recently a lot bigger. i understand your fear of foods, i guess i kind of have the same thing. i was eating a really low calorie diet to get from where i was to where i am (350 to 180 in less than a year). and i want to be able to gain a lot more muscle.... but the only way to do that is to get a little bit of fat back as well while your eating a lot to gain the muscle. but im doing it conservatively, i was eating around 3500 calories for 2-3 weeks and saw zero gain in weight, so im up to 4000 calories about per day, and its hard to tell if theres any real gain or not yet because ive always got food in me. but i can tell visually that im not getting fatter.
the best way to do it, is exactly how you thought already, up it slowly, id say since your intake is so low already only add 100 every 2 weeks until you get what you want. but it depends on what your eating already and what you do for workouts. if you want to gain a lot of muscle then make those 100 calories a good carbohydrate, like oats, which is what i did because iw as getting plenty of protein already. any other info on your current diet, what you eat, and what you do to exercise would be very helpful.