• In a large bowl, cream together butter and sugar until light and fluffy. Beat in egg and vanilla. In another bowl, sift together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet to form a cohesive dough.
• Use a food scale to divide the dough into four portions. Wrap them each in plastic wrap or in a sealable bag, and chill for at least an hour.
• Preheat oven at 350 degrees. Prepare a large baking sheet with parchment paper.
• Pull out a portion of chilled dough. On a far side of the baking sheet, form it into a 12-inch-long stick, 1 inch across. Use fingertips to form a trench down the middle. Spoon jam to fill the trench. Repeat the process with the other three portions of dough, creating long lines on the pan.
• Bake for 18 to 22 minutes, until dough looks set and is light golden brown. Let cool for 2 minutes. Slice each stick 3/4-inch apart to form individual cookies. Move them to a rack to completely cool. Store in a sealed container at room temperature.

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