There are recipes in the Failsafe books and a specific Failsafe recipe book that I found very useful.
The first thing I did was get him to eat vegetable soup, as most of the veg are pretty unpalatable - so I started with a couple of spoonfuls before the main meal and after two weeks he and his brother were starting their evening meal with a small bowl of veg soup (I used swede, leek, cabbage, brussels, celery, lentils, split peas, potatoes in varying proportions; you can do a good lentil soup or leek and potato or celery soup if they like celery). I worked on green beans and cabbage as accompanying vegetables too as they're on the failsafe list.
He had a peeled pear every day. I made lots of casserole type things as well with chicken, beef or lamb, including swede, potato, leeks etc.
He stuck to porridge or basic unflavoured wholewheat cereal eg Weetabix, Rice Pops; I avoided cereals with glucose-fructose syrup or barley malt flavouring and went for the ones with actual barley malt.
I got a breadmaker and made my own bread. I did try pear jam but he wasn't keen so mostly ate just butter on bread.
They're allowed maple syrup and a little golden syrup and citric acid (lemon flavoured) and vanilla as a flavouring - so I made vanilla cakes, lemon cake (with citric acid), a lemon-flavoured squash substitute from the recipe book. I made pancakes and waffles, plain iced cakes, lots of oaty biscuits etc.
It seems unhealthy at first as you're denying them fruit and feeding them syrup soaked pancakes, but he was much healthier and I made sure he got his veg in other ways.
Got to go now but happy to answer more questions!