For the meringue base, preheat the oven (electric oven: 100 °C/circulating air: 75 °C/gas: see manufacturer). Line a baking tray with baking paper. Beat the egg white until stiff, gradually adding sugar and 1 pinch of salt.
Continue beating until the sugar has dissolved and the mixture is shiny. Finally stir in lemon juice.
Stir in food colouring briefly so that pink streaks form. Pour the egg whites into a piping bag with a large star-shaped spout. Spray 24 flat rosettes (each approx. 3 cm Ø) onto the tray.
Leave to dry in a hot oven for about 2 hours. Take out and let cool down.
Break the chocolate into pieces for the filling. Melt carefully in a hot water bath, let it cool down for about 10 minutes. Whisk the butter with the whisks of the mixer for about 6 minutes until white and creamy.
Gradually stir in the chocolate while it is still liquid.
Fill chocolate cream into a piping bag. Pour onto the smooth underside of 12 meringue rosettes. Place the remaining rosettes on top and press down lightly. Leave to set in a cool place (not in the fridge!).
Keep in a cool place for 2-3 days.