Wet Mix

• ¼ cup plus 2 tablespoons heavy cream
• 2 egg yolks

Dry Mix

• 1½ cups buckwheat flour
• 1 cup all-purpose flour
• 1 cup sugar
• 1½ teaspoons kosher salt
• 6 ounces (1½ sticks) unsalted butter, at room temperature

Finish

• 2 tablespoons sugar
• 2 tablespoons poppy seeds
• Egg whites from egg yolks above

1. Measure the cream and egg yolks into a small bowl—no need to whisk—and set aside.
2. Sift the dry ingredients into a large bowl, pouring back into the bowl any bits of grain or other ingredients that may remain in the sifter. Add the softened butter to the dry ingredients. With your hands, squeeze the butter into the flour. After the butter is mostly blended in, add the cream and egg yolks. Continue squeezing the mixture until a crumbly dough forms. Scrape the dough onto a well-floured surface and, using the palm of your hand, smear the dough to fully incorporate all the ingredients.

3. Divide the dough in half. Roll each piece of dough into a log that is 8 inches long and 1¾ inches wide, flouring the dough and work surface as needed. Chill the logs for 2 hours. If the dough is more lopsided than round, you can gently roll the dough again after 15 minutes or so.

4. In a small bowl, stir together the sugar and poppy seeds and pour onto a plate. Brush one log very lightly with the egg whites. (I find it easiest to stand the log on one end as I brush it.) Roll the log in the poppy seed mixture until it is entirely covered. Repeat this process with the remaining log and chill while the oven is heating up, or wrapped in plastic for up to 5 days.
5. Place two racks in the upper and lower thirds of the oven and preheat to 350°F. Line two baking sheets with parchment. Slice the logs into ⅛-inch wafers. Arrange the wafers on the baking sheets.
6. Bake for 15 to 17 minutes, rotating the sheets halfway through. The wafers should be dark golden-brown, with a darker ring around the edge, and smell quite nutty. Cool the cookies on a rack and repeat with the remaining wafers.
7. These wafers are best eaten the day that they’re made, but they’ll keep in an airtight container for up to 1 week.