Preheat your oven to 300°F (150°C) and prepare two baking trays lined with parchment paper.

In a large mixing bowl, add room temperature egg whites and a pinch of salt. Beat the egg whites on medium speed until soft peaks form, about 2-3 minutes. Gradually add the granulated sugar while beating at high speed until glossy and stiff peaks form.

Sift together powdered sugar, finely ground almonds, and cornstarch in a separate bowl. Gently fold this mixture into the meringue using a spatula.

Transfer the meringue mixture into a piping bag fitted with a round tip. Pipe 3-4 inch wide discs onto the prepared baking trays, smoothing the tops gently.

Bake for 40-45 minutes until firm and crisp on the outside. Keep the oven door slightly ajar during the last 10 minutes to prevent cracking, then let them cool inside the oven.

In a chilled mixing bowl, whip the heavy cream on medium speed, gradually adding powdered sugar and vanilla extract until soft peaks form. Gently fold in toasted sliced almonds.

Select half of the baked meringue discs and spread or pipe the cream filling on top. Place the remaining discs on top to create a sandwich effect.

Dust the assembled cookies with powdered sugar and sprinkle extra sliced almonds on top before serving.