Frozen puff pastry is the key to this quick cheese and onion tart

Few frozen ingredients are as versatile as store-bought puff pastry. You can get all fancy — cutting it into shapes, topping them with multiple layers of precooked ingredients, crimping and brushing with an egg wash — before baking into little party appetizers. Or you can keep things very basic, leaving the dough whole — you can even skip rolling it — then adding a few key players that turn it into a quick main course that tastes a lot more complicated than it is.

The latter is my preferred way to go, for obvious reasons.

Even I was surprised, though, at this recipe, which shows just how simple the approach can get, while still netting great results. The key to this cheese and onion tart is the combination of three basic ingredients: Dijon mustard, for a layer of sharpness; shallots, which become wonderfully sweet as they bake; and aged cheddar, which offers richness, depth and browning. A sprinkling of fresh thyme and a little ground pepper complete the picture.

No cutting, no rolling, no crimping, no egg-washing. The most time-consuming activity, besides the hands-off oven time, is the 10 to 15 minutes it takes you to peel and cut a load of shallots, but it's smooth sailing from then on out. After assembling the tart, you bake it on a baking sheet lined with parchment, which not only makes for easy cleanup but allows you to slide the whole thing off the pan for cooling and cutting.

It's a stunner, really, thanks to all those layers of butter (or oil, if you're using a vegan puff pastry) and dough that cause the pastry to do exactly what its name promises: Puff several inches high in the oven. As it cools, the edges stay high while the rest of the tart sinks under the weight of the toppings, which means that when you cut it and take a bite, it tastes like the crispiest, most buttery pizza ever. You'll feel simultaneously as if you hardly did a thing and as if you performed — or at least supervised — a miracle.

Use an all-butter variety such as Dufour unless you want the tart to be vegan, in which case use vegan cheese and Pepperidge Farm pastry. (That brand's sheets are smaller, so you'll want to reduce the amount of shallots, mustard and cheese by about 25 percent.) Cut into 12 or more squares for an appetizer, and 6 for an entree (if you're using Dufour pastry; 4 if you're using Pepperidge Farm), and serve the latter with a crunchy green salad.