I've read a lot of the threads on gravy, but would like to start a new one to see if I can understand the chemistry / mechanics of making a good basic gravy. Because I didn't, this past Thanksgiving. :-( Here's what happened (apologies in advance - this will be long):
The day before Thanksgiving, I made a make-ahead gravy with the intention of adding the drippings after the turkey came out of the oven. Following instructions and videos I found online, I used equal parts butter and flour, and cooked the roux for about 5 minutes, whisking constantly, until I got a paste-like consistency. I then added homemade turkey stock in 1-cup increments, and cooked the gravy for 40 minutes. I intended to cook it for only 15 minutes, but it tasted floury, so I kept cooking it. As the gravy thickened, I added more stock, hoping that the floury taste would dissipate. It never did entirely, and I eventually said "it's good enough". (I used 6 T. of butter to 6 T. of flour, and started with 6 cups of turkey stock; I probably ended up using 10-12 cups of stock.)
The next day, we took the 2 turkeys out of the oven and off the grill and combined the drippings. After defatting the drippings, I added some to my warmed-up make-ahead gravy. My friend deglazed the roasting pan and drippings with some white wine and leftover water from boiling the potatoes for mashed potatoes, and used a cornstarch slurry to thicken the gravy. Her gravy was delicious, and was so easy to make. Mine still tasted floury and had a slightly gritty texture, although the drippings did add a lot of flavor. I ended up adding some fresh lemon juice, which helped a little, but not much. I was really disappointed in my gravy, especially after all that advance work.
I know there are lots of ways to add flavors and make your gravy "your own", but what I'm really trying to understand is the proper (fail-safe) way to make a basic gravy. Here is what I'm wondering:
1) Why did my gravy turn out floury tasting? (This has happened to me in the past, too, so I must consistently be doing something wrong.)
2) What are the advantages (or disadvantages) of a cornstarch slurry? My friend is from the Midwest and she said that's how they always make gravy. Is this a regional thing?
3) I know that a butter / flour Roux is a French classic, and it's supposed to be easy to make. But if it's that easy, what am I doing wrong?
4) Why make a roux, which contains so much fat, when you can just shake up a cornstarch slurry or even a flour slurry? Does the butter make that much difference to the flavor?
Any and all opinions and advice, the more detailed the better, are welcome. Thank you!