Espresso Tonic

I once spent a summer in Norway as a teenager, so I know firsthand the experience of unending daylight. Looking back, I can imagine how those sunlit nights might inspire a person living there full time to drink a lot of coffee. Then again, I could also imagine the interminable darkness of winter driving an equally heavy need to caffeine. Actually, I don't need to imagine it, I can confirm it—Nordic countries consistently dominate lists of worldwide coffee consumption.

When you drink that much coffee, it's inevitable that boredom with the same old cup of Josef, as they'd maybe (probably don't) say in Scandinavian tongues, would lead to innovation. That kind of coffee inventiveness is how espresso tonic came to be. Today the iced drink has worldwide fame and is a popular item on coffee shop menus everywhere, and it all supposedly started in 2007 after a couple of coffee pros from Koppi Roasters in Sweden got to playing with some leftover tonic.

My own relationship with home-pulled espresso started several months ago, after I received a Gaggia Classic espresso machine through work for longterm testing. I was lucky enough to get a one-on-one espresso brewing lesson from none other than Jesse Raub, my former Serious Eats colleague and coffee pro extraordinaire. As much as I love the straight shots of espresso I can now pull whenever I remember to preheat my machine, I too have been seeking more ways to drink them. While steamed milk for cappuccinos and cortados is always a pleasure, when the warm weather sets in, iced drinks beckon, and espresso tonics are one great option for that.

On the surface, an espresso tonic couldn't be simpler—all you're really doing is combining espresso and tonic on ice—but as with simple things, the devil lies in the details. I called up Jesse to get some tips on making a better espresso tonic. "One thing with espresso tonic is that the good versions are almost always slightly churched up," he told me, suggesting I think about it like constructing a cocktail. This could mean, for example, blending the base ingredients into a pleasant ratio and then adding an aromatic ingredient and/or sweetener for balance and interest.

The combination of espresso and tonic on their own is a particularly compelling one. The tonic offers its carbonated fizz, of course, which, when chilled, makes for a very refreshing drink. Tonic is also a very well balanced soda, with a sweetness that isn't cloying matched with a light quinine bitterness. All in all, it integrates beautifully with the bitter edge of coffee.

Still, there are some things to consider for a better espresso tonic. These tips and serving ideas come via Jesse as well as things I've thought up during testing or come across as I've tasted espresso tonic variants at coffee shops whenever I've seen them.

Answers to the Most Pressing Questions About Espresso Tonics

• What's the best coffee for espresso tonic? "An espresso tonic is probably not going to taste great with a traditional dark roasted espresso blend," says Jesse. "Those are chocolatey and roasty, but for this drink you want a coffee that's more fruit forward and floral. Ethiopian coffees work really well." If in doubt, check the flavor and roasting notes on the coffee bag; they should indicate whether the beans are more in that darkly roasted territory you'd want to avoid or not. A fruity, slightly more acidic coffee will generally pair better with the sweet-bitter notes of tonic.
• Does the tonic matter? As one of your only two main ingredients, the tonic does indeed matter. I'm a big fan of the Fever Tree brand tonic waters and often drink them in place of sweeter sodas at home, though feel free to use whatever your preferred brand is. Just make sure to chill your tonic before building the drink. If you pour room-temp tonic on ice, it'll just melt more of the ice faster, diluting the drink prematurely.
• What are the best ratios of tonic to espresso? This is largely a question of personal preference and will also depend on the flavors of the tonic and espresso you're using, though in my testing I've found that I prefer a more generous pour of the tonic water relative to the espresso. My recipe below calls for four times as much tonic to espresso by volume, though this should be considered a rough starting point, not a hard rule.
• Can I use another kind of coffee instead of espresso? Yes, you can experiment with other strongly brewed coffees, such as cold brew or Aeropress coffee, though ratios may shift depending on what you use.
• To float or not? One popular way to serve this drink is with the espresso "floated" on top of the tonic, so that there's separation visible through the glass. This has an effect on the experience of tasting the drink as well, since the initial sips will be espresso-heavy and then it will transition to more tonic as you get deeper into it. You can alternatively blend the two so that the drink is more balanced and consistent from beginning to end. There's no right answer here; the float looks cool and may be appealing to some drinkers, whereas the blended version may appeal to others. The photos in this article show it as a float because it looks nice, but I personally lean more towards blending the drink for that consistent balance of flavors. If you do want to make the float, add the tonic to the glass first, then gently pour the shot on top; you can use a spoon to help break the fall of the espresso as it goes into the glass, reducing the degree to which it mixes into the tonic, though I've also noticed that the tonic's carbonation helps prevent mixing all on its own, the bubbles pushing up against the espresso as it enters the glass.

Flavoring Variations for Espresso Tonic

The basic combination of espresso and tonic is really a blank slate, but, as Jesse said to me, "there are ways to make a much more compelling recipe than just espresso and tonic on their own." That doesn't mean the recipe has to be complicated, it's possible you're already sitting on ingredients that would lend themselves to a more spruced-up version of the drink.

One thing you will likely want to add is a touch more sweetness to your glass on top of whatever the tonic itself is delivering. The best way to do this is with a splash of simple syrup—equal parts by volume of sugar dissolved in water. Syrups, though, lend themselves to flavorings. Here are some flavoring ideas to consider, whether in syrup, garnish, or extract form:

• Oleo-Saccharum: This syrup made by macerating lemon rinds in sugar is often an excellent match for espresso and tonic (just think of all those lemon peels served alongside espresso in Italy).
• Floral Syrups: You can infuse food-grade flowers like lavender, jasmine, and lilac into simple syrup (see our lavender simple syrup recipe for the basic technique), and then add those floral notes the the drink. You can also take a shortcut by adding a drop or two of orange flower water or rose water to simple syrup.
• Fruity Syrups: The fruity notes of coffee make a fruit-flavored syrup a good idea. We have recipes for cherry pit syrup, pineapple syrup, and mango syrup to get you started.
• Maple Syrup: No need to make a syrup from scratch—maple syrup tastes great in this drink. While I haven't tried them, you could also play with other syrups. Would a touch of Lyle's Golden Syrup work? A judicious drop of molasses? Honey? Maybe, I don't know, but it'd be fun to try.
• Extracts: A dash of good-quality vanilla in extract or paste form or almond extract would all add interest to the drink.
• Citrus Wedges and Peels: The aromatic oils of citrus peel can add significant aroma and flavor the the drink with little effort. A lemon peel twist is great, though grapefruit is another pitch-perfect flavor for espresso tonic. And of course you could add a wedge for a bit of the juice as well.

Use the above ideas as a jumping off point, then look around your kitchen and see what else might be fun to try.