I was looking through the wikia, and I found an awesome food item for Mages.
This food gives an extra hundred points of magika and 25% bonus to magicka regen for 720 seconds. Alchemy cannot reproduce this effect, the only ingredient that fortifies and regenerates magika (not restore) is Jazbay Grapes.
However, Red Mountain Flowers, Briar Hearts, and Ectoplasm all have two effects in common, Restore Magika and Fortify Magika. However, I strongly doubt that you can make a potion that fortifies as much for as long, and you'll never be able to restore as much magika as 25% regeneration over 720 seconds can get you.
The trouble with the Fondue is that it requires Moon Sugar. I've only ever been able to find that stuff on Khajit caravans or on the random drug dealers. The special cheese may be a little tricky, but there's plenty of it around. Ale is a nonfactor, the people of Skyrim swim in it.
Compared witht the three ingredients in the restore/fortify magika potion I mentioned above, There is a severly limited supply of Ectoplasm and Briar Hearts. The former only occurs in specific areas and never in large amounts. The latter is only found on boss level enemies, again in no great supply. Red Mountain Flowers are not hard to find, but they are useless without one of the other two ingredients.
Fondue saved my life. I was fighting Rahgot the Dragon Priest with my mage, and he and his army of Draugr killed me twice. I decided to experiment with the food, and it felt like I had used Highborn. I spewed Chain Lightning all over the place and had enough Magika left over to Thunderbolt Rahgot to Oblivion. I hope he ended up in Dagon's Deadlands.
Surprised at this effective food, I started looking for other food items that might be useful. That's when I came across Beef Stew
This food has the effects of Fortifying Stamina, while Regenerating it at a rate of 2 points a second. As with the Fondue, Alchemy has no direct answer to it. You can't make a potion that Fortifies and Regenerates Stamina. You can't even make a deal effect Stamina boosting potion, like a Restore and Regenerate.
Beef Stew is not as powerful a food as the Fondue. It provides less fortification and less total regeneration. I feel it makes up for that with its common ingredients. All four of them are not only commonly found, you can gather them in any town for less than 20 Septims.
Beef Stew is not as awesome for warriors as Fondue is for mages, but it will definatly increase your number of power attacks, shield bashes, and your sprint time.
I've found three more food items worth making, which are also hard to make in alchemy. I'm not going to write essays on them here, but I will leave you the links.
One last thing, the Homemade Meal is awesome. It is worth getting hitched just so you can have a few around.
I don't always give advice about Skyrim, but when I do, its worth trying.
Stay thirsty my friends.