Tonight I made the same mistake. I decided to make Simple Perfect Enchiladas from Pioneer Woman.
And all went well, for the first five minutes. I whisked together the flour and oil, then realized I needed chicken broth and enchilada sauce! The broth wasn't a big deal, but I would have preferred to have it made before. The sauce was a bit more complicated. I had some in the pantry, but it was badly outdated (we don't usually use enchilada sauce). I used it anyway, hoping it wouldn't taste as bad as it smelled. :) It did. I set about to make a new batch. Since I had no more enchilada sauce to use, I mixed together some tomato juice, water, flour, and several seasonings (basil, oregano, etc.). Against all odds, it actually turned out good! Then again, I assume it's good. I don't know what it was supposed to be like. :)
Then came the actual assembly. It was a messier process than I had anticipated.
I didn't use the chilies, olives, green onion, or cilantro. I think they would have been better if I had. They were, however, still very good.
I learned two things: first, Pioneer Woman has a much bigger pantry than I do, resulting in my often having to substitute/skip ingredients. And second, wow, she can make some really good dishes, often with more steps than I usually do. I was surprised (because......I failed to read the recipe thoroughly and realize what it all involved!).