If you occasionally venture into upscale cafes, you may have noticed baristas making pour-over coffees, a process which requires them to spend several uninterrupted minutes slowly pouring hot water from a long-spouted kettle into a basket of grounds, basically doing what a countertop coffee maker was designed to do, but by hand. They often pour in a spiral pattern, which depending on your perspective may strike you as functional, meditative, or twee. It's a very hands-on and time-consuming way to make coffee, so much so, in fact, that many cafes are too busy to do it in house.

Done right, though, a pour-over can taste like the best cup of drip you've ever had. In fact, the whole pour-over process is perhaps the perfect coffee-making method for one group in particular: control freaks.

With the right equipment, pour over offers the possibility to dial in almost every element in the brewing process; you can heat a set amount of water to a specific temperature (Fellow's Stagg kettles are lovely for this), weigh beans then grind them to a specific size (typically "coarse sand"), pour the beans into a paper filter in what's called a dripper, put the dripper over a carafe or cup and start pouring. Many baristas like to do a short initial pour to "pre-infuse" or wet the grounds, then pause for about 30 seconds as the coffee lets off carbon dioxide with a bubbling effect known as the "bloom." At this point, some break the next few minutes into a few pours and pauses, while others just go slow and steady, both styles working to keep all the grinds saturated.

Up to now, though, coffee brewers were at the mercy of the dripper design, particularly the size of the holes at its base which govern the flow of liquid through the dripper, and thus, how much time the grounds spend being exposed to the hot water. It's an important variable: too much contact produces flavors you don't want from overextraction. Too little contact and not only do you have weak, thin-flavored coffee, but you're also wasting beans.

December Coffee

Enter the December Dripper ($60), which, by increasing the number of moving parts in a typical dripper from zero to one, allows you to control the flow instead of forcing you go to with it. That part is a pivot between the bottom collar (the flattish ring at the bottom that keeps the whole shebang from falling into your cup) and the cone on top. It's pretty clever. By squishing a gasket between the two parts, users can twist to open or close a series of holes that help control the flow of liquid. This also allows more latitude for making larger and smaller batches of coffee.

For comparison's sake, I ran 190 ml of water through an unfiltered Kalita Wave 155 (the Wave is considered by many to be the dripper of reference), which took about 23 seconds to empty out. On the December Dripper, the same amount of water took about 44 seconds on setting one (four holes), 24 seconds on setting two (eight holes), and 18 seconds on setting three (12 holes). You can also close all the holes, allowing a pre-infusion of grounds that doesn't let any liquid through until you change the setting.

Well, almost none: many users, myself included, report a slight leaking problem, particularly at that closed setting, which can be a bit of a mess. Wrecking Ball Coffee Roasters, the tiny company which makes the December Dripper along with Korea's CSBC, made an endearing video of how to fix it, by tapping it flat with a hammer—Yikes!—and more recent productions are said to have addressed the issue.

I brought the dripper over to Seattle's revered Empire Espresso and ran a set of tests with co-owner Ian Peters. First, we set our constants: 18 grams of Kuma Coffee's Guatemalan "Felicidad," fresh-ground to that coarse-sand consistency, with 250 ml of water heated to 204 degrees Fahrenheit.

We pre-infused the grounds (aka "wetting") with the flow wide open on setting 3, then moved on to the main pour, which made for a cup with a clean, light, and juicy flavor, and a pleasing acidic finish, making it Peters's immediate favorite. My preference was the next cup, where we set the dripper to the slowest flow rate (number one), which gave it more of the toasty notes I like.

"With either of our favorites you'd say, 'That's a great cup of coffee,'" said Peters.

Next, we tried Empire's own Ethiopia Guji Kercha roast. We made one cup with the Kalita Wave 155, then one cup at each of the December Dripper's settings, with Peters giving them a 30-second pre-infusion, then a slow, steady pour until the mug was full. Unsurprisingly, the Kalita and the number two position on the December Dripper had similar results. While the wide-open setting (number three) was almost visibly too fast a pour for this setup and it produced a thin and vegetal cup, the slowest setting (number one) made for a sweet, smooth coffee with a pleasing acidity.

The day before, Peters had wondered aloud if he really saw the value in the Dripper, but now, the value was clear.

"I don't know what you'd do to make a better cup," he said. "I'd buy this just to keep it on the slow setting."

At home, I tested with a darker roast, which isn't always the favorite of pour-over fanatics, but as it's my preferred roast, it made for less distracting testing for me. In three trials, the only variable I changed was the openings in the December Dripper. Setting one—the slowest flow—was overly bitter and setting two was a bit too toasty, while setting three tasted rounder with a pleasing aftertaste, a clear favorite. Wrecking Ball's Nick Cho's rule of thumb is to try to have a dark roast pour done in under three minutes and lighter roasts between three and four minutes.

Now that I had my preferred flow rate for my dark roast, I could choose to call it good or keep on tinkering, locking in the dripper's setting and tweaking a different variables like bean weight, ground size, or water temperature. Regardless, as in the testing with Peters, a little bit of experimenting in my own kitchen had already led to a great cup.

There are a few other things worth mentioning: In the stainless steel model that I reviewed, a lack of contrast between the indicator marks and the walls of the dripper made it tricky to which setting I was on, but more recent models use black laser etching for better visibility. There is also a special gasket available for purchase for an extra-slow flow.

Whether or not you should buy one depends on what kind of coffee fanatic you are. If you're in it for the ritual and already have a pour-over setup that feels dialed in, why bother? If however, you're more into the control and enjoy mixing up the variables, the December Dripper is a great tool to take on the quest to find your version of perfection.

Food writer Joe Ray (@joe_diner) is a Lowell Thomas Travel Journalist of The Year, a restaurant critic, and author of "Sea and Smoke" with chef Blaine Wetzel.