I went through a spell long ago of thickening all sauces with cornstarch because of the foolproof, lump-free results. While fine for Asian or fruit sauces where you prize that translucent, glossy nature of such a sauce, it just isn’t satisfying in both flavor and texture for those meat gravies that you want for mashed potatoes and stews, so I eventually went back to the fat-flour roux for those sauces.
One Thanksgiving in grad school, while I was in the cornstarch mode, I was in the kitchen making the gravy—and it was a huge pot of it—and I made my cornstarch and water mixture for that last step before eating. I poured some of it in, because I wasn’t quite sure how many cups of stock/drippings I had in the pot, and it rose up like one of those grade school volcano experiments and flowed over the sides into the burner and then receded. I stared at it, wondering why that happened, cleared the burner and poured in some more. Same volcanic action. Same confused stare. Then it hit me that I had grabbed baking soda instead of cornstarch. I didn’t call to the living room for help; I just stared some more and wondered what to do. What else could I do? I mixed up the right ingredients and thickened the gravy and we ate it, getting our post-dinner bicarbonate during dinner.
Luckily, it tasted fine, but it may be one reason I often read labels out loud just to confirm to myself what I’m doing.