The short answer
Whisky and food work together when strength, sweetness, and roasted notes align. Small tastings will get you further than fixed rules based on origin or age.

Food first, then the bottle
A very powerful whisky will overwhelm delicate food. So for a mild dish, choose something lighter; with bold roasted flavors, the pairing can be bolder too. And you don't need whisky throughout an entire meal — one well-chosen pairing often achieves more.
The order helps: food first, then the whisky. Choosing a dish to match a bottle rarely works well; the other way around almost always does. At high strength, a drop of water is worthwhile — neat alongside food, cask-strength whisky can come across as an interruption.
Cheese: fat helps, salt sharpens
An aged hard cheese often pairs well with nutty or spicy cask notes. Blue cheese is far more intense — better to try it first in a small portion. Set a non-smoky bottle alongside. It comes down to the specific cheese and the specific bottling, not simply the word "whisky."
Fat is your ally here: it takes the edge off the alcohol's bite and lets sweeter cask notes come forward. Salt works the other way, sharpening the contrast. That's why an aged hard cheese often works with a sherry-cask whisky right away, while blue cheese remains a gamble.

Chocolate: cocoa content decides
Try chocolates with different cocoa contents side by side. Very sweet chocolate makes a dry whisky taste sharper, while very bitter chocolate intensifies the bitterness. Vanilla and roasted notes can bridge both sides, though never with certainty. Try each on its own first, then take a small bite just before the sip.
When both are smoky, nobody wins
Smoky whiskies can pair well with grilled or smoked food. But they can also overwhelm each other. Set a fruitier, less smoky bottle alongside — then you'll notice whether you prefer the pairing or the contrast. Write down exactly which combination it was; "smoke with grilled food" is too vague for next time. And set out water and something non-alcoholic just as naturally.
A test beforehand: nose the whisky and think of the dish. If both conjure up the same image, choose something else. Contrast gets you further here than similarity.