Step 1

Prepare and refrigerate the pie dough.

Step 2

Roll the dough as you would for most pies, about ⅛-inch thick or a tad thinner. Don’t worry about keeping it nice and round like you normally would.

Step 3

Using a 4-inch-diameter cookie or biscuit cutter, cut the dough into as many circles as possible. Line each cup of a standard 12-cup muffin pan with one of the circles, gently nudging it down into the bottom creases of the pan. Try not to stretch the dough as you work; it can help to use something blunt, like a narrow jar, to nudge the dough. The top edge of the dough circle should come to about the middle of the cup. Gather the scraps and reroll the dough if you need additional ­circles. Chill the pan in the freezer for 20 to 30  minutes.

Step 4

Adjust one oven rack so it is in the lower position, and preheat the oven to 425°F (220°C). Combine the sugar, maple syrup, and butter in a mixing bowl. Whisk briefly. Add the egg, vinegar, vanilla, and salt, and whisk again.

Step 5

Set the muffin pan on your work surface. If you’re using the fruit or nuts, put a few pieces in as many of the shells as you wish, but don’t crowd them. Use a ladle or ¼-cup measuring cup with a handle to divide the filling evenly between the shells.

Step 6

Bake for 15 to 18 minutes, until the filling bubbles and darkens somewhat.

Step 7

Transfer the pan to a rack and cool for 5 minutes, then carefully run a butter knife around the edge to loosen each tart. Let the tarts cool in the pan, then remove. Store, refrigerated, in a single layer in a covered tin or container, but let them come to room temperature before serving.