It's all kind of circular for an author hunting for the first publication. Publishers prefer to work on contract as do authors so they're not writing what they cant' sell. Looking at a list of cookbook publishers, they want a short, usually one page proposal. If they're interested, they'll probably want to see a manuscript sample of a chapter or two.
First, define your topic. It's probably not just cooking unless you're writing a general cookery book. And I can't recommend you start there unless you can keep the book SHORT. it's too hard of a sell unless you're well established or recognized as an authority. And there's lots of them out there already. Save that for your third or fourth book. You need to focus, prune and find an underserved segment that's still large enough to sell to profitably. Because that makes your book easier to sell and more appealing to the publisher.This is your pitch, or hook. a first time author's success is mostly about the pitch. The manuscript just clinches the deal.
Most will want your sample file in an e-format of some sort. Word document or at least that format, maybe PDF if you are intent on pictures in the submission. You pictures better WOW if you want them in your submission. You'll want it to print out well, but you don't need to stress over layout and formatting too much. Submissions really haven't changed a lot since the typewriter days.
→ Use a 1″ margin on all sides
→ Use a title page, set up the same as the title page in your package (see page 159).
→ Don’t number the title page. Begin numbering with the first page of the text of the book, usually the introduction, prologue, or chapter one.
→ Use a header on each page, including your name, the title of your novel in all caps, and the page number.
→ Start each new chapter on its own page, one-third of the way down the page.
→ The chapter number and chapter title should be in all caps, separated by two hyphens: CHAPTER 1—THE BODY.
→ Begin the body of the chapter four to six lines below the chapter title.
→ Indent fives spaces for each new paragraph.
→ Double-space the entire text.
→ Use a standard font, 12-point type. Times New Roman, Arial, or Courier is fine.
→ Use 20-lb. bond paper.
Now there's content there on printed format, but just make sure your electronic file conforms to that as you won't do a printed copy for a while most likely for editing feedback. Really, that's plain simple instructions and you don't have to worry about formatting or pretty. What you have to be able to show is that you can organize, write and present well within that structure.
They won't rewrite your book for you. You'll do that with the editing feedback if they want to proceed to a full manuscript. You just have to make sure your sample chapters are excellent so you get to the full manuscript point.
Most cookbooks have a simple formula:
Intro content about the chapter topic, 1-10 paragraphs usually, rarely longer. Maybe a few technique notes that are common for the chapter.
intro about why the recipe is important, significant, good, history or what not
Repeat from the Recipe name again and again until your chapter is full.
That's really all there is to most cookbooks. If you want to expand from that and wax more heavily on theory and technique, your pitch will be harder most likely and easier to pitch to the publisher in a later book.