1. Prepare 2 parchment-lined baking sheets large enough to hold 30 x 4cm/1 1/2” diameter shells each.
2. Mix ground almonds, powdered sugar (and cocoa powder, if using) in a bowl, then grind in a food processor until extra fine. Process in batches if necessary.
3. Sift into a large bowl, re-grinding any larger pieces.
4. Add 50g egg whites and mix thoroughly. Add food coloring, if using. Set aside.
5. In a clean bowl (or stand mixer with balloon whisk), beat the other 50g egg whites to stiff peaks.
6. In a saucepan, heat granulated sugar and water on medium-low to 118°C/244°F without stirring.
7. While whisking constantly on low speed, slowly add the cooked sugar mixture to the beaten egg whites, pouring it down the inside edge of the bowl.
8. Whisk at high speed until cool (about 3 minutes). The mixture should increase in volume, become firm and shiny, and form a beak when you lift the whisk.
9. Scrape the meringue onto the almond mixture and combine until you have a homogeneous batter.
10. Transfer the mixture to a piping bag fitted with a 7–9mm/#10–#12 plain round tip. Pipe 60 equally sized rounds (about 4cm/1 1/2”) onto prepared sheets.
11. Tap the baking sheet to release air bubbles. Press down any tips with a damp fingertip.
12. Let rest at room temperature for at least 20 minutes until slightly tacky.
13. Preheat oven to 150°C/300°F/Gas Mark 2.
14. Bake for 18 minutes per sheet, turning halfway through.
15. Remove from oven, let cool on parchment for at least 30 minutes, then remove from parchment.
16. Store in an airtight container at room temperature if not filling immediately.

For the filling

1. Process berries until smooth, then press through a fine mesh sieve into a saucepan.
2. Add lemon juice, sugar (and powdered pectin, if using), and bring to a boil. Cook at a rapid boil according to package directions. Cool completely, stirring occasionally.
3. Pipe or spoon filling onto half the shells, top with remaining shells, and press gently.
4. Store in an airtight container in the refrigerator for at least 24 hours before eating.