Start by lining a cookie sheet with a silicone mat or parchment paper, ensuring it's flat and smooth. Preheat your oven to 280°F (138°C) for baking after the shells rest.

In a food processor, pulse together the powdered sugar and almond flour until fine. Sift into a bowl to eliminate lumps, then whisk in the poppy seeds.

Whip room temperature egg whites until frothy. Gradually add granulated sugar while whisking until stiff peaks form, about 5-7 minutes.

Gently fold the meringue into the dry ingredient mixture using a spatula until smooth and consistent.

Transfer the batter into a piping bag fitted with a round tip. Pipe 1-inch discs on your prepared sheet, spaced about an inch apart.

Allow the piped shells to rest at room temperature for about 1 hour to form a skin.

Confirm that your oven is preheated to 280°F (138°C).

Bake for 15 minutes, rotating the sheet every 5 minutes for even baking.

Remove from the oven and let them cool completely on the baking sheet.

In a heatproof bowl over simmering water, whisk together sugar, lemon juice, egg, and egg yolk until thickened, reaching a temperature of 180°F (82°C). Let cool before folding in whipped cream.

Pipe the lemon curd filling between two macaron shells, creating a sandwich.