Preheat the oven to 350°F (180°C), or 325°F (160°C) for fan-forced. Lightly grease or spray 2 large trays and line with parchment paper.

Roast the blanched almonds for 7 minutes on a small tray, shaking once halfway. Cool the almonds on the tray. Bash or blitz the cooled almonds using a food processor or a ziplock bag and rolling pin until they resemble coarse sand with some small lumps.

In a large bowl, cream the softened unsalted butter and white sugar until light and fluffy. Beat in the large egg and vanilla extract until well combined.

In a separate bowl, whisk together the plain flour, baking powder, and cooking salt. Gradually add the dry ingredients to the wet ingredients in three batches, mixing until just combined after each addition. Beat in the prepared almond bits.

Roll the dough into approximately 30 balls, each about 2 tablespoons (use a #40 scoop if you have one). Slightly flatten each ball. Brush the tops of the flattened cookies with the lightly whisked egg white and then sprinkle with almond flakes.

Bake for 20 minutes, or until the biscuits are light golden around the edges. Let them cool on the trays for a few minutes before transferring to a wire rack to cool completely.