1-First, preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper. This sets the stage for even baking and easy cleanup. If you're adapting for dietary needs, check your ingredients now.

2-Next, in a food processor, pulse two-thirds of the shelled pistachios until coarsely chopped, then set them aside. Combine the remaining pistachios with 2 teaspoons of flour and pulse until finely ground to create a nutty flour base.

3-In a medium bowl, whisk together the pistachio flour, the remaining 1 cup of flour, and salt until well blended.

4-Beat the softened butter and sugar on medium-high speed until light and fluffy, which takes about 3-4 minutes, then mix in the vanilla extract.

5-Reduce the mixer speed to low and gradually add the flour mixture until a dough forms; if it's dry, add a small splash of milk or water to help it come together.

6-Whisk the egg white until frothy, then roll the dough into 1-inch balls. Dip each ball into the egg white and roll in the crushed pistachios for coating.

7-Place the balls 2 inches apart on the baking sheets and use the end of a wooden spoon to make indentations in the centers, reshaping as needed.

8-Bake for 15-18 minutes until the bottoms are lightly golden, rotating the pans halfway through for even cooking. Let them cool on the sheets for 3-4 minutes before moving to racks.

9-Dust the cookies lightly with powdered sugar once cooled.

10-Heat the jam in a small saucepan until it boils, then spoon about ½ to 1 teaspoon into each indentation and let it set completely.