It’s become fashionable these days to vilify butter and cream but if you want your wine to shine bring them into play. There’s almost nothing better than a rich creamy sauce to show off a fine white burgundy and whisking a little butter into a red wine sauce will set your Bordeaux off a treat.
The reason, of course, is simple (if unglamourous): fat is palate-coating which means it diminishes the effect of both acid and tannin in wine. It also makes a dish milder and more mellow allowing the character of the wine to shine through. It can mitigate bitterness or sharpness in other ingredients: creamed or buttered spinach (or spinach combined with cheese or cheese sauce, for that matter) is much easier to match than a side of spinach on its own as is a tomato sauce with a touch of cream.
Cream also illustrates the principle of compare or contrast that many people talk about in food and wine matching. An oaked chardonnay has a creamy quality of its own that mimics the creamy quality of a sauce. Or you can go for the contrast of a crisp (but intense) wine that will freshen the pairing. Unoaked Chablis, for example, tastes good with creamy sauces too (especially with ham - a favourite dish from the region).
Cream added to a fruit dessert will also help bring a dessert wine into play. The sharpness of lemon, for example, can often play havoc with dessert wines but with cream folded into or served with the dessert you have many more options.
Buttery sauces like hollandaise or beurre blanc also support heavyweight whites. Meursault for example is a fine match for eggs benedict - if you can face it at that time in the morning! They will however strip the character from lighter, sharper whites - a Pinot Grigio or Albarino won’t benefit from a buttery sauce and vice versa. And a classic French-style purée of potatoes into which lashings of butter has been beaten will make a tannic red taste more mellow.
You’ll also find that the addition of cream, butter or yoghurt can help match a wine to a spicy dish like a curry, diminishing their heat. Kormas, butter chicken and other curries served with yoghurt stirred in or served alongside are all more likely to be wine-friendly. It seems to have a particularly good effect on riesling, accentuating its sweetness and floweriness.
The only exception to this rule is cheese which not only doesn't always assist a wine match but can pose problems of its own due to its myriad different flavours. But that's another story.