Cream the butter and sugar: In a large bowl, beat the softened butter and granulated sugar with a hand mixer or stand mixer on medium speed until light and fluffy, about 2–3 minutes. Scrape down the bowl.

Add egg and extracts: Mix in the egg, vanilla, and almond extract (if using) until fully combined. The mixture should look smooth and creamy.

Combine dry ingredients: In a separate bowl, whisk flour, baking powder, and salt. Add the dry mix to the wet in two additions, mixing on low just until the dough starts to come together.

Adjust consistency: If the dough looks crumbly, add milk 1 teaspoon at a time until it holds together but isn’t sticky. You want a soft, pliable dough that forms a ball easily.

Chill briefly: Cover and chill the dough for 20–30 minutes. This helps prevent spreading and makes shaping easier.

Preheat and prep: Heat the oven to 350°F (175°C). Line two baking sheets with parchment paper.

Shape the cookies: Scoop 1 tablespoon portions and roll into smooth balls. If using sanding sugar, roll the dough balls lightly in it now. Space them about 2 inches apart on the sheets.

Make the wells: Use your thumb, the back of a 1/2 teaspoon measure, or the end of a thick wooden spoon to press a shallow well into the center of each ball. Don’t press too hard; you want a neat indentation without cracking.

Bake the shells: Bake for 8–10 minutes, until the edges are set but still pale. Remove the tray and gently press the wells again, if they’ve puffed, while the cookies are warm.

Fill and finish baking: Spoon about 1 teaspoon lemon curd into each well. Return to the oven and bake another 3–4 minutes, until the curd looks glossy and the cookie edges are just turning golden.

Cool completely: Let the cookies rest on the sheet for 5 minutes, then transfer to a wire rack to cool. For a neat look, avoid moving them while the curd is hot.

Optional garnish: Once cool, dust with powdered sugar, drizzle with melted white chocolate, or add a whisper of lemon zest for extra aroma.