These toaster tarts may remind you of Pop-Tarts, but without the overly-sweet, processed taste. Instead, you have a flaky, buttery crust enveloping a jammy center. My version is half whole-wheat filled with peach jam that has been thickened with a bit of corn starch. This step prevents your jam filling from having a total meltdown in the oven, creating a mostly empty pocket (sad).
If your jam is especially runny (first consider buying a better quality jam…), but a 5-minute simmer in a small saucepan with a tablespoon of cornstarch and a teaspoon of water or lemon juice will do the trick to reduce and thicken. This is a good tip for any jam-filled cakes, cookies, etc. to prevent filling seepage or spillage.
1 cup whole-wheat flour
1 cup all-purpose flour
1 tablespoon sugar
1 teaspoon salt
1 1/2 sticks unsalted butter
2 large eggs
3 tablespoons ice water
1/2 cup fruit jam
1 tablespoon cornstarch
Preheat oven to 375F. Line a cookie sheet with parchment paper. In the bowl of a food processor, whiz together dry ingredients. Cube cold butter, then add to the bowl and pulse a few times.
Whisk 1 egg with 3 tsp ice water, and drizzle into food processor while pulsing until mixture clumps together. Transfer dough to a lightly-floured surface, roll out to 1/4 inch thick rectangle.
Using a sharp knife or pastry wheel, cut as many equally sized rectangles as you can - about 12 (for 6 tarts). Whisk together 1 egg with 1 tablespoon milk or cream, brush along the perimeter of 1/2 the rectangles.
Mix jam with cornstarch, and spoon about 1 tablespoon in the centers, then gently place the remaining pastry on top, and crimp the edges with a fork. Brush the tops with remaining egg wash and sprinkle with sugar. Transfer to baking sheet and bake for about 20 minutes until golden brown.