Failed pan sauce didn't thicken and tasted far too much of wine

The biggest reason your sauce didn't thicken is that you didn't have much of anything at all in the pan that will gelatinize and help trap the water molecules present in the sauce. Starches (flour, cornstarch) will provide some of this, as will a liquid like stock that contains some dissolved collagens. But wine and water by themselves will have very little thickening power. At minimum, you'll want to add a teaspoon or two of cornstarch to your wine/water mix and shake in a covered vessel - this is called a slurry and will thicken fairly quickly, but you need to be careful not to overcook it.

For a more traditional (and in my opinion, much tastier) pan sauce, try the following steps:

First, make sure that you pour off any excess oil - you want no more than about a tablespoon or so left in the pan, less if you're adding butter.

Second, heat the pan by itself for a few moments, which will help dissolve the fond (little flavorful brown bits left in the pan) during the next steps. If you want to add your onions, this would be the time to do so.

At this point, if you want a really thick sauce, add your butter, and sprinkle in a very small amount (no more than the amount of butter you've added) of regular flour. Whisk this well for about a minute until it seems to thin slightly. What you're doing here is creating a quick roux that will help thicken the final mixture. You can skip this step if you like.

Next, carefully add your wine and wait a moment to help burn off some of the alcohol flavor. Whisk or stir with a fork for few seconds to help dissolve the flavorful fond. Then, add stock - this is very advisable especially if you didn't create a roux. Stock both has more flavor than water and (especially with meat stocks) contains collagen, producing a more velvety-tasting final sauce. Store-bought stocks are fine, and are a great pantry item to keep around; you don't have to make your own.

At this point, stir in your other flavorings (herbs, etc.) and reduce the sauce over medium-low heat until you're happy with the texture. A good way of checking is to dip in a spoon, flip it over, and run your finger across the back. If the sauce doesn't fill in the track left by your finger, it's good to go.

When reducing a sauce, keep in mind that the flavors you add are going to be intensified. Wine reduces very well, meaning that its flavor absolutely becomes stronger the more it is reduced.

The water in liquids evaporate, that's what reduction is all about. Fats don't evaporate. If you start a sauce with 1 part fat to 3 parts liquid and reduce it 2 parts, it's going to end up half fat. That's a pretty greasy pan sauce. The oil doesn't add much flavor to the sauce, what does add flavor are the crunchy brown bits that stick to the bottom of a stainless steel skillet when browning meat. Be sure to get that flavor in your sauce.

Next time, pour off (or spoon off) all but about a tablespoon of fat, up to a couple of tablespoons if you're going to make a roux. Saute some onion or shallot in that fat. If you want to thicken with flour, now is the best time to add it. Add a tablespoon or a bit more of flour to the skillet, and cook it with the onions or shallots, stirring constantly, until it starts to brown. This is now a roux that will thicken your final sauce. Deglaze the pan (scrape up all of those great bits) with just a hint of wine mixed with a broth to match your meat. Since your last sauce tasted too strongly of wine for your taste, start with a small amount of wine and use a bit more with every sauce until you hit just the level of "wineyness" you want. Be sure you're using a wine you like, if you wouldn't drink it, don't cook with it. Use low sodium canned broth (or stock) or use homemade unsalted broth. Also at this point, be sure to add any juices that have collected under the meat you have set aside. Add salt when you are done, like other flavors salt becomes more concentrated as the sauce reduces. A reduction made with broth that tasted perfectly salted will be inedibly salty once reduced.

A great thing to keep in your fridge is Better Than Bouillon reduced sodium chicken base. In a pinch you can always use it in a sauce, keep it handy. Plain water does not make for a good sauce base.

So now, reduce away. It's done reducing when you say it's done. When it's done reducing is the time to taste for salt. Also add pepper, herbs, lemon juice, mustard, Worcestershire, whatever. If you care to, you can add butter at the very end. Whisk in cold butter cut into small chunks. That will give you an emulsion with a nice mouth feel. You can also thicken the sauce more by adding some cornstarch slurry to your simmering sauce. Be careful, do it a tiny bit at a time, you're kind of screwed if you over thicken.

Good luck. With practice pan sauces will become second nature. No recipe required.

I would recommend next time, cooking the onion in the pan juices first. Then as the onion becomes browned or clear depending on taste, add a tablespoon of flour and whisk it in with the juices until it is a slightly tan color. Then add the wine/water mixture and herbs, whisking constantly until it reaches the desired thickness, remembering also that it will continue to thicken some after you take it off the heat.

Another idea using your original mixture (with the onion and herbs added) would be to add one tablespoon of corn starch dissolved in one tablespoon of water, added when mixture is at a near boil, return to a boil whisking constantly for one minute. Remove from the heat and stir occasionally, after 5 minutes it should be a thick consistency.

Measurements may vary based on how much oil was originally used. In any case, don't give up. Gravy is not an exact science and takes some practice. And sometimes, the mistakes taste amazing too!