In answer to my earlier post, here is an efficient way to level (or more precisely "tier") a cook/farmer combination. What's efficient for you may be different. For me, money was no issue (Total cost was under 900s for the farmer, 6g500s for the cook). I tried to minimze time as reflected in the total number of recipe invocations (3,000 (including harvests) for the farmer, 1,700 for the cook). Total time around 13 hours.

Note that tiering a farmer is much slower than a cook. When you plant, harvest, and process, you get no Craft XP for the harvesting. When I tried planting more than 8 fields at a time, some would disappear before I could harvest them, and harvesting requires an interaction for each field. Once you have the ingredients, a cook can run off hundreds of items, stopping only when the tools need repairs. Farmers get fewer Craft XP per item, and the same Craft XP for all things at the same tier. After you make the things needed to support the cook tiering, you can make a pile of whatever you like to tier the farmer.

Farmer production varies a lot. Although there is an average harvest per field at each tier, it may produce much more or only one. What I show below is the number of items you need to produce for the cook, not the number you plant. Fortunately, the mats are cheap and can be purchased, so if you need more you can plant more.

For cooks, recipes T6 and above are mostly dropped. You will need to find a T7 [item]Bowl of Spring Water Recipe[/item] and a T8 [item]Eastemnet Crumbs Recipe[/item]. They are generally available in the AH (except at the very moment you need them, plan ahead!). The other recipes are basic or purchased from NPC cooks/farmers.

During the Expert T3 tier for both, when you reach Expert Proficiency, you must stop and do some quests to reach the Artisan T4 tier. You can get the quests from the farmer/cook NPCs. They will send you to Michel Delving. Do the farmer first, because you will need Artisan strawberries to complete the cook's quest. After the quests, you can continue with the Expert tier.

Here's the plan:

Apprentice Farmer
75 [item]Fresh Carrot[/item]
224 [item]Mushroom[/item] (Used by Master Cook)

Apprentice Cook
75 [item]Cooked Carrot[/item]

Journeyman Farmer
210 [item]Bunch of Oats[/item]
95 [item]Tater[/item] (Used by Artisan Cook)

Journeyman Cook
105 [item]Bowl of Oatmeal[/item]

Expert Farmer
174 [item]Green Onion[/item] (79 for Expert Cook, 95 for Artisan Cook)
Miscellaneous things during the quests
2 [item]Bunch of Strawberries[/item] for cook after reaching Artisan.

Expert Cook
79 [item]Bowl of Hearty Stock[/item]
78 [item]Beef Stew[/item] (you'll make one more in cook's quest)

Artisan Farmer
Nothing specific needed from this tier, grow anything

Artisan Cook
95 [item]Bowl of Chicken Stock[/item]
95 [item]Stew of Kings[/item]

Master Farmer
282 [item]Golden Shire Tater[/item] (112 for Master Cook, 170 for Westfold Cook)

Master Cook
112 [item]Bowl of Beef Stock[/item]
112 [item]Cream of Mushroom Soup[/item]

Supreme Farmer
300 [item]Bundle of Mint Leaves[/item]

Supreme Cook
300 [item]Bowl of Water[/item]

Westfold Farmer
340 [item]Bunch of Leeks[/item]

Westfold Cook
170 [item]Bowl of Leek Stock[/item]
170 [item]Bowl of Spring Water[/item]

Eastemnet Farmer
285 [item]Bunch of Rye Berries[/item]

Eastemnet Cook
285 [item]Bag of Eastemnet Crumbs[/item]

Since the farmer doesn't constrain things, this is also the most efficient way to tier a cook alone, assuming you can get access to the needed mats. The cook alone is under 5 hours. If the farmer needs only proficiency, not mastery, it will save over 5 hours.