In a large mixing bowl or the bowl of a stand mixer, add butter, sugar, lemon zest, and lemon oil and mix on high speed until fluffy and well-combined.

In a separate bowl, stir together flour, poppyseeds, and salt.

Add the dry ingredients and mix on low until the mixture resembles coarse breadcrumbs.

Use your hands to bring the mixture together, kneading gently until a loose dough forms.

Shape into a log, approximately 8 inches long and about 1 1/2 inches in diameter.

Wrap log in clingfilm/plastic wrap and chill in the refrigerator until firm, at least 1 hour, or overnight.

Preheat oven to 180° C / 355° F. Line a half sheet rimmed baking tray with parchment or a silicone mat.

Unwrap log. With a sharp chef’s knife, cut into slices, each about 1/2-inch thick. You should have about 16 slices total.

Arrange slices on prepared tray.

Freeze cookies on tray for 10 minutes. (If your tray does not fit in the freezer, layer the slices between squares of parchment and freeze the stacks instead.)

Bake in preheated oven for 20-25 minutes, or until lightly golden brown around the edges.*

Cool on tray 10 minutes, then transfer to a wire rack to cool completely.

Store lemon poppyseed shortbread cookies in an airtight container at room temperature for up to 5 days.