To be honest the friendship system in the game is so tedious that I don't fool with it and part of me balks at the idea of buying friendship anywhere. However, unless I am mistaken this is the only real way to get All the recipes. It would be nice if we could buy a cookbook or even a series of cookbooks. In addition to a universe goods and resource catalogue this is something I would love to see someoen create.
This isn't necessarily helpful, but if no one is able to get this mod going for you, there's a really easy way to farm friendship that only requires talking to someone once a year... just give them a loved item on their birthday and it's practically an automatic 3 hearts. In a few years you'll have all the recipes. Not exactly what you're looking for, but an easy way around it if the purchasable cookbook idea doesn't work out.
I like this idea! I know its a pain when you don't have all the recipes and the TV cooking channel can only get you so far. When I have some time I'll look into it.
Try this one. http://www.nexusmods.com/stardewvalley/mods/631/? I don't know if you can buy all the recipes here because I haven't used that part but you can buy a lot of stuff.
I've written a mod to buy cookbooks if you are still interested The mod is called Buy Recipes and you can grab the the latest version as a .zip if you want. Buy Recipes is a Stardew Valley mod which lets you buy cooking recipes from the SMAPI console. Each week on Sunday a new set of up to five recipes will be available to buy. These will be recipes that you do not already own. Prices are listed next to each item.
