How one takes their coffee is an extremely personal matter, and I am always hesitant to tell people they are “doing it wrong,” particularly because coffee pedantry is the worst type of pedantry.
But my boyfriend was doing it wrong, and I had to tell him. Like Samin Nosrrat, he takes his coffee with “enough milk so that it looks like Haagen-Dazs coffee ice cream.” He also adds an amount of sugar I previously had assumed was suitable only for hummingbirds — but the flavour is not the problem. Obviously, there’s nothing wrong with sweet, creamy coffee, but the man was adding the cold milk — straight from the fridge — to his coffee before adding the sugar, dropping the temperature of the beverage and preventing the sweetener from going fully into solution, leaving a pile of granules at the bottom of his mug.
It’s a matter of solubility, you see. Sugar does not dissolve well in cold liquid — that’s why we have simple syrup for iced coffee and cocktails — so you need that heat from the fresh coffee, particularly if your ratio of sugar (solute) to coffee (solvent) is very high. Obviously, adding cold dairy decreases the overall temperature, making your coffee less effective as a solvent. This is why you should always add your sugar before your cream, ensuring all of the sugar dissolves.
(In an effort to quantify, I did a comparison where I added a sugar cube to an cup of coffee and another sugar cube to a mixture of 3/4 cup of coffee and 1/4 cup of cold milk the sugar cube in the creamy coffee took 26 more seconds of stirring to dissolve than the sugar cube in black coffee.)
Of course, this all varies with exactly how much of each you add to your morning beverage, and how much hot coffee you start with, but adding things in this order ensures the sugar is fully dissolved. If you add only a tiny splash of cream, you aren’t changing the temperature as drastically, and a little extra stirring will probably get the job done. Conversely, a tiny amount of sugar is still fairly likely to dissolve in a not-quite-as-hot cup of coffee, simply because you are dealing with a small amount of solute.
If you’re a fan of raw or turbinado sugar (which tend to have a larger granule size), the extra heat is even more helpful. (If you drink it black, I’m not sure why you clicked on this and if you are Joel, I don’t know how to help you.) So add the sugar to hot coffee, give it a stir, and then dollop in the cream. Sugar and cream are good, but grit is not.