What is bake two group serving of cookies?

It means create two servings of cookies.

Go to the store to buy the cookie book so you can learn how to make them since I don't believe you learn it just by leveling your cooking skill.

When you've finished reading the book to learn how to make them, go to the stove and click the "serve cookies" I guess.  Do this twice, and put them in your inventory so no one takes them.  Then deliver them or whatever it is you're supposed to do with them.