I realize I’m posting Christmas cookies a week after the event, but I can never seem to find time to blog about anything in the midst of my annual pre-Christmas baking madness. And it’s still technically Yuletide until tomorrow, January 1, so it’s not too late for Christmas cookies! Especially when they are as good as these ones.

About eight Christmases ago I made a lemon-pistachio sandwich cookie filled with lemon frosting that Nate particularly liked, and he’s been asking me to make them again ever since. I remember being less impressed with them: I found them too sweet, not lemony enough, and their roll-and-cut construction meant they were finicky as heck to make. But I agreed that the concept had potential, so this year I set out to re-engineer them into the cookie of my dreams.

I started with the Cook’s Illustrated French French Butter Cookies recipe – a traditional sablé cookie with a crisp, sandy texture – and added some lemon zest and chopped pistachios. As a bonus, these are slice and bake cookies so they are much faster and less fiddly than rolling out and cutting each individual cookie. For the filling, I turned to Tartine’s lemon cream recipe, a lemon curd cooked until very thick then blended with lots of butter, resulting in what is practically a lemon curd buttercream. I knew this would give me the creamy lemon kick I wanted without resorting to a sickly-sweet confectioner’s sugar frosting.

All went according to plan until I got to the lemon cream, which seemed like it would be too runny to stay put between the cookies. But I persevered, piping the lemon cream in dollops on half the cookies and gently sandwiching them with a second cookie. I tried one right away and it tasted great but crumbled into a hundred pieces and the filling squished out everywhere. At this point I was feeling a bit uneasy about this cookie experiment – I had invested much time and ingredients and they were on track for turning into a mess – so I put them a container and let them mellow for 24 hours, hoping for a Christmas miracle to firm up the lemon cream and soften the cookies. And the next day, the miracle came through and I ended up with some of the most delicious cookies I’ve ever made: a perfect combination of creamy and sandy textures, mellow pistachio against tart lemon with a bit of extra sweetness from a drizzle of white chocolate. Worth every moment of uncertainty and definitely worthy of a place in future Christmas baking marathons!

Lemon Cream Pistachio Sandwich Cookies

Lemon cream from Tartine. Lemon-pistachio cookies adapted from Cook’s Illustrated. Makes about 35 small sandwich cookies. Click here for a printable PDF of the recipe.

Lemon Cream

In a heat-proof, non-reactive medium bowl, whisk together:

3 large eggs

1 large egg yolk

3/4 cup sugar

pinch salt

1/2 cup + 2 tbsp lemon juice

Place the bowl over a pot filled with a few inches of barely simmering water (without the bottom of the bowl touching the water) and cook, whisking, for a loooooooong time, until the mixture turns into a very thick, scoopable curd (it will be about 180˚F on an instant-read thermometer).

Remove the curd from the heat and allow it to cool for a few minutes to about 140˚F, whisking occasionally. While it cools, cut 1 cup unsalted butter into cubes (about 1 tbsp each).

Pour the lemon curd into a blender, or use an immersion blender, and begin blending the curd. Add the butter, one cube at a time, allowing each to emulsify before adding the next.

The lemon curd will turn creamy, pale, and thick. If it doesn’t, you may not have cooked the lemon curd enough in the first step – just place it back over a double boiler and cook until VERY thick, then blend in a few more tablespoons of butter until thick and creamy.

Press a piece of plastic wrap directly to the surface to prevent a skin from forming, and let it cool to room temperature before filling the cookies (or you can refrigerate until needed – bring it back to room temperature so it pipes easily). This will make more than you need to fill the cookies, but no one ever got mad about having extra lemon curd, which can be kept in the fridge for up to 5 days (if it lasts that long).

Lemon-Pistachio Cookies

In the bowl of an electric mixer, place:

10 tbsp unsalted butter, softened

1/3 cup + 1 tbsp granulated sugar

1/4 tsp fine sea salt

Place a fine mesh strainer over the bowl and press 1 hardboiled egg yolk through the strainer into the bowl.

With the paddle attachment, cream everything together on medium speed until light and fluffy. Add:

1 tsp vanilla extract

zest of 1 lemon

Measure out 1 1/2 cups all purpose flour. Add half of it to the butter-sugar mixture and mix to combine. Stir in 1/2 cup finely chopped pistachios, then add the remaining flour and mix until just combined.

Scrape down the bottom and sides of the bowl with a spatula and give the dough a few final turns/folds with the spatula to make sure everything is evenly mixed.

Divide the dough in half and form each half into a 6-inch cylinder. Begin pressing the cylinder flat and turning it 90 degrees to make a square cross-section, with each side about 1 inch wide and the log about 9 1/2 inches long. Wrap in waxed paper and chill for at least 1 hour, until firm.

When ready to bake, preheat the oven to 350˚F (325˚F convection) with the racks in the upper and lower third positions. Slice each dough log into 1/4-inch thick slices with a large, sharp knife. Arrange the slices about 1 inch apart on a parchment paper or silicon mat-lined baking sheet.

Bake for 10-12 minutes, until pale golden brown and slightly darker at the edges, rotating the racks front to back and top to bottom half way through baking. Cool for about 5 minutes on the baking sheets, then transfer the cookies to a cooling rack.

Assembly

Place about 1 cup cooled lemon cream in a piping bag, and pipe about 1 teaspoon on the bottom of half the cooled cookies.

Top with a second cookie and press gently so the cream reaches the edges of the cookies.

Melt about 1/2 cup chopped white chocolate and place it in a piping bag. Pipe a squiggle of white chocolate on each cookie sandwich. Sprinkle the cookies with 2 tbsp finely chopped pistachios.

Let the cookies sit until the chocolate sets, then layer them between waxed paper in an airtight container and store them somewhere cool and dry (not the fridge) for at least 24 hours for the textures to meld. Will keep at a cool room temperature for about 4 days.