How much of a recipe needs to be changed so that I am not breaking any copyright laws?

What you are proposing to do is dangerous: copyright includes not just the right to publish the material as is, but the right to create "derivative works"--or to publish a version that has a few strategic changes. If you adapt a specific published recipe from another person, you are violating copyright; while yes, there is clearly some point at which the recipe has been sufficiently changed so that it is no longer the original in any regards, even a derivative version of the original, where exactly is that point is  not readily or easily defined.

What you can do much more safetly is develop your own recipes, even if they are based on other's recipes, so long as you draw from multiple sources. For example: take choclate chip cookies. There are likely thousands of recipes  out there, varying slightly in ingredients, proportions, measurements, cooking time and temperature. If you look at a number of recipes and then come up with your own which is inspired by all the different ones you've reviewed--but NOT based on any one of them--that would be safe--you would not be creating a derivative work from any one copyrighted recipe.

This in turn means that it's much safer to publish your own version of recipes for fairly common dishes--meatloaf, chocloate ships, lasagna--then for very unusual or signature dishes, especially of famous chefs. For example,  say that Bobby Flay has a recipe for "pulled gator" which he did for a Louisiana restaurant on one of his shows--if you published that recipe, substituting sugar cane for brown sugar, you'd be violating his copyright, since it's safe to say that's the only "pulled gator" receipe you could be adapting.