In a large mixing bowl, beat the softened butter and granulated sugar with an electric mixer for 2–3 minutes, until creamy and slightly lighter in color.

Add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl as needed.

Add the flour mixture in two or three additions. Mix on low speed just until a soft dough forms. Do not overmix.

Divide the dough into two equal portions. Cover and refrigerate for 30–60 minutes.

Preheat the oven to 350°F. Line a large rimmed baking sheet with parchment paper.

Shape each portion of chilled dough into a log approximately 12–14 inches long. Place both logs on the prepared baking sheet, leaving at least 3 inches between them.

Flatten each log until it is approximately 3 inches wide and ½ inch thick.

Using your finger, the handle of a wooden spoon, or the back of a teaspoon, press a groove lengthwise down the center of each log. Do not press all the way through the dough.

Bake the unfilled cookie logs for 10–12 minutes, until they begin to set but have not yet browned.

Remove the baking sheet from the oven. If the grooves have puffed up, carefully press them down again with the back of a spoon.

Spoon the jam evenly into the grooves, being careful not to overfill them.

Return the baking sheet to the oven and bake for another 8–10 minutes, until the edges are lightly golden.

Let the cookie logs cool on the pan for approximately 10 minutes.

While they are still slightly warm, use a sharp knife to cut each log crosswise or slightly diagonally into 1-inch-wide cookies.

Transfer the cookies to a wire rack and allow them to cool completely before serving or storing.