What would you plant for both cooking and medicinal purposes? Also would want as many perennials as possible.

strictly double duty plants? 

mint should always be in there, but you first need the knowledge of what herbs to use for what ailment, and how to process and dose them properly to avoid making things worse.

I'm thinking herbs that can help with fever, pain, upset stomach. No, don't have to be double duty but I'd hate to plant a bunch of stuff I may never use if they can't also be used for cooking. Right now we've got lavender basil rosemary and a few kinds of mint planted. But I want to expand our garden some next spring.

Actually don't have to be strictly herbs. Any perennial that could have medicinal use is a possibility.

I REALLY think you should actually know how to process and dose herbs before doing what you want to do. Once you know what is for what, you won't need to ask what to plant 

Waiting for my lesson

lol

You could start with some books on Amazon, but I don't know which ones are best. 

My mother just finished up classes to become an herbalist. Took her about 18 months. 

I would at least start with some books, because you need to know which plants are truly useful, what part of the plant to use and when (many do have a particular "season" to harvest and process) and which parts of the plants are toxic, and exactly how to use it all. That means making tinctures, teas, extracts, etc..

For cooking, just start with the basics. Rosemary, dill, basil, maybe some fennel. As far as medicinal, the only ones I've used medicinally was spearmint and Texas tarragon (tagetes lucida), chew up and swallow a few sprigs with a stevia leaf to make it more tolerable, helps me with digestion.

Lavender oil makes me sleepy. You could probably crush up a bit and rub it on your feet to help you sleep.

My mother is out not doing much today, I will ask her to write down some safe herbs and their uses that I will forward on.

Yeah my mother gave me a herb book to look at. She cut all our basil(2 plants) and it made I think 4 quarts of pesto.

How about stinging nettle?

Our herb garden has basil, rosemary, sage, thyme, oregano, dill, parsley, cilantro, and borage. (Basil is lemon basil, Italian basil, and sacred basil.  Different kinds of flavor for cooking, and the sacred basil is said to be one of 5 plants that actually repel mosquitoes).

We also have coriander, calendula, mint (apple mint and spearmint, I think), beebalm, marigold, dandelion, broad lead plantain, and rue.  

We are trying to source some real roses for rose hips (high in Vitamin C).  

Our top two herb books are:
Rodale's Illustrated Encyclopedia of Herbs, Claire Kowalchik and William H. Hylton

The Complete Herbs Sourcebook, David Hoffman

We also just purchased:
Growing At-Risk Medicinal Herbs, Richo Cech

Herbs and Herb Lore of Colonial America

Our next herbal purchases are going to be:
Culpeper's Complete Herbal and English Physician

A Physician's Desk Reference for Herbal Medicine

The Rodale's Illustrated is a must own, in my opinion.  It has in depth knowledge of all usable herbs, with history, folk lore, real medical data, and everything you need to know for growing, cultivating and preparing.  It also has articles on dangerous herbs, companion planting for the garden, and different garden styles.  For example:
Borage:  History, uses, Culinary use, Ornamental use, Companion planting, cultivation, as well as a description, growing range and conditions, and some chef tips.

The Complete Herbs Sourcebook is like an old time herbal medical reference.  It is specific to actions, best applications, and precautions.  For example:

Borage has the constituents:Saponins, mucilage, tannins, essential oil.  It's actions include: Diaphoretic, expectorant, tonic, anti-inflammatory, galactogogue.  It give instructions for how to prepare and all that, so it's a neat reference to have.