Preheat oven to 350°F. Line baking sheets with parchment paper or a Silpat.

In the bowl of a stand mixer fitted with the paddle attachment, beat 1 cup salted butter (firm but not cold), 2/3 cup granulated sugar, and the seeds from 1 vanilla bean (or 1 1/2 tsp vanilla extract) on medium-high until pale and fluffy, about 4 minutes.

Add the 2 egg yolks and mix until incorporated. Transfer the egg whites to a small bowl and set aside.

Reduce mixer speed to low and slowly add 2 1/4 cups all-purpose flour. Mix until the dough comes together (it may look dry at first).

Form the dough into a ball, wrap in plastic, and refrigerate for 30 minutes.

While the dough chills, place 1 cup finely chopped unsalted pistachios in a shallow bowl and whisk the reserved egg whites until frothy.

Scoop the chilled dough 1 tablespoon at a time and roll each portion into a smooth ball.

Dip each dough ball into the frothy egg white to coat, then roll into the chopped pistachios so the sides and bottom are coated, leaving a small uncoated circle on top for the jam.

Place the coated balls on the prepared baking sheets (up to 15 per sheet). Using your thumb or the back of a teaspoon, press a clear indentation into the center of each ball without pressing through.

Fill each indentation with a heaping 1/2 tsp of the 1/2 cup strawberry preserves.

Bake in the preheated oven for 14–16 minutes, until edges are set and bottoms are lightly golden. Let cookies rest on the baking sheet for several minutes, then transfer to a wire rack to cool completely.

Melt 4 oz white chocolate or semi‑sweet chocolate in a heatproof bowl set over simmering water, or in the microwave at 50% power in 30-second intervals, stirring between intervals until smooth.

Put the melted chocolate into a piping bag or small zip-top bag, snip a small corner, and drizzle the chocolate over the cooled cookies. Store cookies in an airtight container.