Gillie Cookie Recipe

Prepare

Preheat oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone mats.

Cream the butter and sugars: in a large bowl or stand mixer fitted with the paddle attachment, beat the softened butter, granulated sugar, and brown sugar on medium speed until light and fluffy, about 2–3 minutes.

Add egg and vanilla: add the egg and 1 tsp vanilla extract, mixing until combined and smooth, scraping the bowl as needed.

Combine dry ingredients: in a separate bowl whisk together the all-purpose flour, baking soda, and 1/2 tsp salt.

Incorporate dry into wet: with the mixer on low, add the dry ingredients in two additions until just combined. Do not overmix.

Fold in chocolate chips: with a spatula, fold in the semisweet chocolate chips evenly throughout the dough.

Portion dough: using a cookie scoop or spoon, portion the dough into 12 even balls (~1.5 tablespoons each). Place them 2 inches apart on prepared baking sheets. These will be sandwiched later, so make sure they’re uniform in size.

Bake: bake in the preheated oven 9–11 minutes, until edges are golden but centers still soft. Rotate pans halfway through for even baking.

Cool: remove from oven and let cookies cool on baking sheet 5 minutes, then transfer to a wire rack to cool completely. Allow to cool fully before assembling so custard does not melt.

Warm the milk and cream: in a small saucepan over medium heat, warm the whole milk and heavy cream until it just begins to steam and small bubbles form at the edges (do not boil). Remove from heat.

Whisk yolks and dry ingredients: in a heatproof bowl, whisk together the 3 egg yolks, 1/4 cup granulated sugar, 1 tablespoon cornstarch, and 1/8 tsp salt until smooth and slightly pale.

Temper the yolks: slowly whisk about 1/3 of the hot milk mixture into the yolk mixture to temper, then gradually whisk the tempered yolk mixture back into the saucepan with the remaining hot milk, stirring constantly.

Cook custard: return the saucepan to medium-low heat and cook, stirring constantly with a wooden spoon or silicone spatula, until the mixture thickens and coats the back of the spoon, about 3–5 minutes. Do not let it boil vigorously.

Finish custard: remove from heat and stir in 1 tablespoon cold cubed butter and 1/2 tsp vanilla extract until smooth and glossy. Strain through a fine-mesh sieve into a bowl to remove any cooked bits.

Chill: cover the surface of the custard with plastic wrap to prevent a skin from forming. Refrigerate at least 1 hour until fully chilled and set. The custard should be thick enough to pipe but still spreadable. If too thick, whisk in 1–2 teaspoons milk; if too thin, cook gently a little longer.

Match cookies into pairs: select 6 pairs of cookies that are similar in size. Place the bottoms (flatter side) facing up.

Fill: transfer chilled custard to a piping bag fitted with a 1/2-inch round tip or use a spoon. Pipe or spoon about 2 tablespoons of custard onto the center of one cookie of each pair, leaving a 1/4-inch border around the edge to avoid overflow.

Sandwich: gently press the matching cookie on top, twisting slightly to spread the custard evenly to the edge. Wipe any excess custard from the edges for a clean presentation.

Egg wash (optional gloss): lightly brush the top of each assembled sandwich with a small amount of the egg wash for a subtle sheen. This is optional and primarily cosmetic.

Chill to set: place assembled sandwiches in a single layer in the refrigerator for 15–20 minutes to allow the custard to firm and the cookies to meld.

Finish and serve: dust lightly with powdered sugar if desired and serve. Cookies are best within 1–2 days stored in an airtight container in the refrigerator. Bring to room temperature 15–20 minutes before serving for a softer texture.