You could try a birdie muffin with some of his/her favorites mixed in. Unless your bird has been tested as low on calcium or if you plan on using it as a breeder I wouldn't suggest adding any more calcium. Although when baking birdie muffins you can add eggs shell and all to the recipe. Some say shells can carry salmonella but as lon as the cupcakes are cooked fully with no raw eggs etc the bacteria is killed.
Another recipe is the layered salad mix which our picky cockatoos just love along with our other picky birds. Sometimes it takes them a few days to get interested in it but so far it has never failed LOL!
You can make as much or as little as you need. First layer is greens such as collard, kale, mustard, turnip etc. Next layer is green veggies such as cucumber, green beans, peas, or even herbs like cilantro parsley etc. Next is vitamin A rich veggies like broccoli, sweet potato, carrot, winter squash. Fourth layer is uncooked pasta (mine love the veggie rotini it softens when refrigerated with the veggies). Then a cooked bean mixture such as the 15 bean mix you can buy it in frozen bags or just the dried beans and cook/cool them before layering them. next add fresh fruit with at least some acidic fruit such as apple, orange and grapes (we have also used tangerine, pears and others.) Last layer is a bag of frozen veggies you can use the winter/california mix veggies or the regular mix veggies frozen. The coolness from the frozen veggies also helps keep the food underneath fresh.
For one bird you would probably only use like a butter bowl sized dish. For the rescue as you can imagine we use as many as 7-8 of the large glad bowls. This is good for one week. When getting ready to serve you can take out the amount you want to feed for the day and add some nuts, seeds, or other softer fresh fruits like blueberries, strawberries, or cranberries.
Good luck with your picky eater!